Robin has a huge romantic crush on Starfire, which borderlines nearly on obsessive love. Throughout the series, he resorts to every means possible to win her over. It's hinted that she possibly likes him back, although it is never confirmed until "Mouth Hole".
In "Driver's Ed", while the others (including Starfire) teased and laughed at Robin's results of his driving test, Starfire comforted Robin ("It is okay, Robin. Everyone fails the test of driving", though it doesn't help).
In "The Date"', Robin finally musters the courage to ask Starfire out on a date. While she states she is willing to go with him, she also reveals she has agreed to go on a date with Speedy. Robin desperately tries to win her over, but to no avail, so he ends up deciding to sabotage her date with Speedy. Starfire discovers the truth and is furious with Robin and punches him.
In "Hey Pizza!" Robin had the choice between building a senior center (for the unappreciated seniors) or a community pool (probably see Starfire in a bikini and rubbing sunscreen on her). His crush on her made it hard for him to decide. He ended up building the senior center, but Starfire was willing to model the bikini for him anyways. The bikini ended up being for Silkie, much to Robin's disgust. It could either be that Starfire was messing with Robin's feelings, or most likely because she really didn't know that bikinis are for people and not pets (her naivety of Earth culture).
In "Colors of Raven" when Robin and Starfire are chasing Raven's emotions, Robin was about to kiss Raven's passion (with the idea of putting the emotion inside the prism) but Starfire interrupted the kiss, hinting that she thinks it should be her and Robin kissing.
In "Starfire the Terrible", it is revealed that Starfire does have feelings for Robin, as she shows up about to give him flowers but to her jealousy, he is pretending to kiss the moon, however, when Robin was kissing the moon, he was thinking of Starfire, much to her misunderstanding. In the same episode, she really wanted to be Robin's nemesis so that he would feel better and feel like a "true" hero.
In "Breakfast Cheese", she is elated to see Robin using a means of peace, via flowers, to defeat his enemies, just like she had taught him and the other Titans. Overall, they seem to be close friends, but their romantic relationship hasn't evolved.
In "Be Mine ", she accepts Robin when he asks her to be his Valentine. Then at the Valentines dance, Starfire gives Robin a little kiss on the cheek, much to his elation. Her actual feelings for Robin remain unknown after she said she loved him like "the brother."
In "Sidekick", when Starfire dresses up in a bat costume, Robin uncontrollably drools at the sight of her.
In "Uncle Jokes"', she finds comfort in Robin's arms after Beast Boy and Cyborg kicked her out of their comedic trio. In Grandma Voice she becomes very alert when Robin falls through the window. In many episodes she is seen with a Robin doll on her bed but this could be because she has a lot of superhero dolls. In the episode "Puppets, Whaaaaat?"', at the end after once again the Titans call him a freak for playing his puppets and making kissing sounds thus leaving, Starfire remained at the doorway watching even after the others left. It is also seen that she has a stuffed animal of Robin on her bed.In "I See You"', Robin brings Starfire on a criminal watch (aka "stakeout") which is actually just a trick to get her to kiss him. She never kisses him, but they do find Dr. Light and defeat him. Afterwards, Robin admits to Starfire that the whole thing was a trick to get her to kiss him. She then becomes very angry at him, but Robin quickly redeems himself by saying she turned out to be a great detective. After that being told that, she was calmed and tells Robin not to mess with her alternate disguise, "The Jeff".
Also in "Salty Codgers", Robin and Starfire (when old) were seen slow dancing together.
In "Slumber Party" Robin dares Starfire to date, marry, and form a family with him. But Starfire says that she was going to pick truth. Embarrassed, Robin ask her if she will do all those things but she says "no". Robin gets upset and gets in the blanket fort and starts crying while the Titans stare at him.
In "Baby Hands", Robin says that Starfire is his girlfriend and that's why she is in the team after having his team's memories erased. Robin continues to insist this but Starfire rejects, ignores, and punches Robin. She was not even fazed or shocked when Robin confessed that she is not his girlfriend. She also joins in the other Titans in making fun of his baby hands.
However, in "Sandwich Thief"', Robin asked if she loved him on a lie detector and she said yes, but lied. She claimed she did not want to hurt his feelings which was a true statement. She also said couldn't learn to love him or under any circumstances try to go out with him which both turned up as true. However, this may have changed entirely upon seeing his face in "The Mask", she is the most enthusiastic in seeing his "handsome" face, and even swoons when looking at him.
In "Thanksgiving"', Starfire was the only person out of the Titans to see if Robin was alright after the dinner disaster. She also stated that she was thankful that he was their as leader which cheers him up.
In "Mouth Hole", Starfire gives Robin whistling lessons. While she was whistling, Robin starts to become distracted by her beauty. Robin states that she had beautiful hair and eyes. Starfire hears this and tells him what lovely words to describe whistling. Starfire then says to press their lips together and puckers up as Robin puckers up as well. Robin then tries to kiss her but Starfire grabs his lips and stretches them out, leaving Robin in pain. At the end of the episode, after Robin defeats the H.I.V.E with his new whistling power, Starfire states lovingly that she couldn't know that whistling can be so strong. Robin grabs Starfire by the hand and they begin to dance. Starfire then tells Robin to kiss her. They both pucker up while the other Titans watch in awe. This episode confirms Starfire's romantic interest in Robin for the first time.
In "The Return of Slade", it was said that Robin and Starfire kissed after defeating Slade; although it was off screen.
In "Cat's Fancy", Robin was about to explain his love for Starfire, until she saw a cat. Robin then assumed that he'd need to become a cat for Starfire to love him. They had fun together until Robin realized something: Starfire loves him, but only as a "cat lady". Robin scares the kittens away and throws a can over to Starfire saying that the kittens sadly left. Starfire cries because of the kittens, but Robin cheers her up by dressing up as a puppy. They have fun together again, until Robin got hit by a car.
In the episode "A Farce" it is shown that Starfire likes Robin only like a brother.
In the episode "Batman vs. Teen Titans: Dark Injustice", Starfire played a April Fools' Day prank on Robin. She pretended she wanted to kiss him. Surprised and starstuck, Robin puckers up for the kiss but as soon as Starfire and Robin's lips were about to touch Starfire punches him in the stomach so hard that Robin falls onto the ground. Later, when Robin claimed he will go solo as Nightwing Starfire complimented his long hair and mentioned how beautiful it was. As Nightwing and Starfire were about to kiss they look at (along with the rest of the Titans) at the camera and said "April Fools!"
In the The Art Of Ninjutsu, Starfire finally tells Robin that he's truly the Ninja Master. She also said that she'd been wrong for rejecting his affections for her and is in love with him. Robin cries tears of joy and they hugged. He also said that he knew that they'd end up together and Starfire shushed him and they were about to kiss, but then, her face was taken off, revealing that it was really Beast Boy in disguise, much to Robin's shock and sadness.
In the episode "Booty Scooty" it is shown that she likes and is attracted to his butt and it shows that she thinks he has a nice butt in some episodes.
In Thanksgetting, howbeit, she directly proclaims that she’s not thankful for Robin’s stinky attitude.
In “Beast Girl”, Starfire is bewildered when Robin pushes her male counterpart (whom she takes quite a liking to until having a close-up look into his face and starts laughing) out of Madame Rouge’s palace, further confirming that she doesn’t understand Robin’s crush towards her.
In "I Used to Be a Peoples", Starfire is offended by Robin who trespasses into her room and decides to punish him as a secret agent by activating the time bomb inside her secret diary, and is glad that she has managed to thwart his plan.
In "Little Elvis", after Starfire herself is afflicted by the sin hatred, she appears to be infuriated towards Robin and blasts him with her bolts.
Raven (best female friend)
Starfire and Raven are pretty close/somewhat best friends as they’re the only girls among the Titans and get paired together quite often in many scenes, such as sitting/standing together or teaming up. Starfire, who often regards Raven as her best friend, is predominantly friendly to Raven, but Raven is generally not interested. She frequently tries to reject Starfire, but usually not in a mean way, she just wants to be left alone. Even when she does try to be a little mean, Starfire doesn't understand because of her naivety of Earth culture. Occasionally, Starfire looks up to Raven and often seeks for advice from the latter, as well as willingly follows her orders and sometimes concurs with her. As the series goes on, they seem to become the second pair of close friends aside from Beast Boy and Cyborg.
In "Dog Hand"', Starfire says to Raven's father, redundantly, that she is Raven's best female friend within the Teen Titans.
In "Artful Dodgers", they sing a duet "Team Titans" (spoofed off the original "Teen Titans" theme song, yet shorter and with different animations.)
At the end of Colors of Raven" Starfire gave a little speech about Raven, how it is possible under that "dark" appearance could exist a mix of happy, scared, loving, angry and lazy emotions inside. As well in that episode Raven happy side spend time with Starfire (and Cyborg) the most.
In Caged Tiger, Raven and Starfire have enough with the boys’ stupidity and decide to wait for them on the roof so as to fight Dr. Light, but they end up spending time with him and almost change him for good until the boys interrupted and beat him up, which ultimately ruin their friendship with him.
In Love Monsters, Raven warns Starfire that not everything can be solved with affection and told her not to open the chest containing Twin Destroyers of Azarath. Nevertheless, Starfire quickly neglects Raven’s warning and unintentionally causes the monsters to become stronger. After Starfire gives out insults which weakens the monsters, Raven is proud of how Starfire is mean to the cuteness she can’t handle, but Starfire still gets snapped by her and the boys before giving out a kiss to the monsters again.
In Cool School, when Rose Wilson is holding the Titans at sword-point, Starfire tells Raven that they may not be cool but they are her friends. This displays how Starfire cares for Raven.
In Nean, when Starfire asks Raven to attend the chilli wedding despite knowing the latter has doubts to her engagement with the chilli, Raven rejects by snapping at Starfire at first but then her “nice form” makes her supportive to Starfire’s chilli wedding. Nevertheless, Raven still accomplishes in interrupting the wedding and remarking its dumbness, and after Starfire announces that she doesn’t love the chilli and thanks Raven, the girls share a hug.
In "Knowledge", after Starfire misunderstands yet another Earth saying, Raven offers to teach Starfire about earth customs. She sings Mean What'cha Say to her, to educate her about earth sayings and how they are not to be treated literally. Starfire is very grateful for Raven's lesson, but the following day she still has not gotten the hang of it. To speed things up, Raven gives Starfire a magical necklace which would give Starfire knowledge. However the necklace fills Starfire's head with too much knowledge and turns her into a genius, where she begins to recite facts to ruin all of the other Titans' fun, including several of Raven's past times. Eventually they discover Starfire's head has swelled up with knowledge and is on the verge of exploding, to which Raven admits it is all her fault. She joins the other Titans to shrink down into the T-Sub and journey into Starfire's mind to destroy the knowledge and save her. After destroying Starfire's Knowledge, Raven apologizes to Starfire and she forgives her.
At times, Raven and Starfire's relationship can be tested as shown in "Caramel Apples", where they had a small fight between them, over Raven's dad. Other than that, they are pretty close and even pretended to play a role of being each other's fathers for the rest of the day.
In "Boys vs Girls", they both teamed up with each other (due to being the only females in Titans Tower) to compete against the male Titans to prove which gender is more superior than the other. Together, they worked as a team and won every challenge effortlessly, sealing the bet. They both can be quite annoyed with the boys whenever they act disgusting or arrogant.
In "Dignity of Teeth", she, along with the other Titans, decide to ignore Raven's advice about teeth having the source of dignity and lose all their teeth forever until they have nothing but gums. The Titans needs to spend more money, so they attempted to "borrow" Raven's. Starfire attempted to suck Raven's teeth out with a mini-vacuum. They entually get their teeth back and apologize for letting their greed get the best of their smiles. She, along with the other Titans, look in disgust as Raven eats salted teeth.
In The True Meaning of Christmas, when the Titans split up to search for the Naughty List, Raven and Starfire are immediately tempted to eat everything in the house of Gingerbread Man owing to their common love of gingerbread, and later the two have an enjoyable experience... devouring the whole house as well as the poor Gingerbread Man...
In Teen Titans Save Christmas, Raven willingly teams up with Starfire as Christmas elves when Robin assigns them to be the ones to make toys and later they comply with Robin's order on battling with Santa Claus.
In BBSFBDAY, Raven gives the movie tickets that were supposed for Beast Boy to Starfire and offers Starfire to watch a movie about the guys whose moms have the same name, which unknowingly makes Beast Boy jealous.
In BBCYFSHIPBDAY, Raven and Starfire teamed up with Robin so as to help Beast Boy and Cyborg to become best bros again, but their efforts died in vain. Luckily, after Beast Boy and Cyborg reconciled with each other and defeated Cinderblock with their reborn Friendship Friend, the girls and Robin finally realised that friendship can’t be forced and to celebrate the rebirth of the Friendship Friend of Beast Boy and Cyborg, they had a party with the male Titans.
In Bro-Pocalypse, both girls equally find the boys' "bro-out" repulsive and nonsensical. When all the male Titans carelessly injure themselves, Starfire and Raven accompany each other and head to Mount Bro-suvius in order to prevent the Bro-Pocalypse from occurring. At the outset, they act like bros quite unnaturally, yet as their adventure progress, they behave more and more similar to bros, and they even manage to stop the apocalypse regardless bickering earlier, until the boys who come out of nowhere reach the mountain top and ruin their experience of being bros.
In The Scoop!, she grieves after Raven sends her waffle maker into the trash can, feels uneasy when Raven and the boys disapprove her bonding with the scoop and even she goes as far as kidnapping Raven and the boys to coerce them to tell where has the scoop gone before Raven and the boys approve her relationship with the object. The brighter note is that she still forgives Raven and the boys in the end.
In The Groover, Starfire gets dissuaded from rescuing by Raven who claims that Robin deserves comeuppance and never questions Raven's illogical thought.
In Slapping Butts and Celebrating for No Reason, Starfire bonds with Raven by slapping each other's butts.
In "Nostalgia is Not a Substitute for an Actual Story", Starfire thanks Raven who compliments her hairstyle. She also heeds Raven's advice on thanking the two 80s girls who like her hair, although she ends up misinterpreting it.
In some occasions, nonetheless, there have been moments that Raven upsets Starfire. In Nose Mouth, Starfire is fed up with how Raven (who is under the influence of evil magic) has turned her hair golden and in Second Christmas, Raven, Cyborg and Beast Boy are jealous that Starfire gets the chance to celebrate a “second Christmas” so they make up a Second Christmas. After the truth is revealed by the three (owing to Robin’s force), Raven tries to apologise but Starfire goes nuts and Raven lays unconscious with the three boys and Silkie and gets sent to hospital after the Tower gets blown up. Another instance is Secret Garden, in which Raven enters Starfire's garden without permission and Starfire is heartbroken to see Raven draining the life forces of the flowers.
Cyborg (close friend)
In "Pie Bros", Starfire volunteers to organize Cyborg's birthday. It was shown in "Terra-ized" that she and Cyborg enjoy watching morning talk shows together. Starfire is usually willing to play along in Cyborg's silly games and dances (She sang along in the "So Wrong" song, and participated in the Meatball Parties he threw). In "Uncle Jokes", she also sang along in the Uncle Jokes rap. When forced to kick her out of the comedic trio, Cyborg was seen crying.
In "Hose Water", both of them are entranced by the baby bird hatching out of the egg, which inspires the two of them to explore their inner-child. The two engage in exceedingly childish activities throughout the episode, including setting up a fort from pillows, face painting, and drinking hose water. Their excessive childishness eventually leads them to regress to a younger age and get transformed into eggs.
In "Secret Garden," Starfire helps Cyborg to get his stress out by showing him secret garden of peace and quiet. After Starfire goes into a rage he makes another garden for her and apologizes to her to make her feel better. She forgives him for that. This shows that Cyborg and Starfire have a healthy relationship and they both care for each other’s feelings.
In "How 'Bout Some Effort" she cares about Cyborg's and Jinx relationship.
In "Booby Trap House", Cyborg and Starfire not only enjoy making bird sounds, but they are also insane enough to plant the whole tower with dangerous booby traps when Robin goes on a trip with Beast Boy and Raven. They believe that they are behaving like adults, even after their traps have caused Robin, Raven, and Beast Boy many injuries and thrown them in the ocean.
In Flashback, Starfire and Cyborg are seen scribbling doodles on the glass wall of the living room in the beginning of the episode.
Nevertheless, in Caged Tiger, Operation Dude Rescue and Bro-Pocalypse, Starfire displays her strong irritation towards the bro antics of Cyborg and the two other boys. Additionally, in Second Christmas, she is shown to be extremely infuriated to Cyborg after she realizes he along with Beast Boy and Raven have cheated her about Second Christmas.
Beast Boy's street-wise and crafty personality due to his trickster nature makes him the polar opposite of Starfire. Even though both are good friends, Beast Boy has a habit to manipulate her to his advantage. He has also pranks her, most notably in "Ghost Boy" because Starfire is the only one that's naive enough to fall for his pranks.
In "Starliar", after Beast Boy hears that Starfire got invited to the Titans East Dance when the other Titans didn't, he encourages her to lie as to not hurt the other Titans' feelings. The two also practiced lying to the other Titans throughout the episode "Starliar" resulting in the Titans attacking each other out of anger. However Starfire keeps a friendly demeanor with him. They both have a similar personality of being positive, fun-loving, and native but Starfire is more mature than him.
In "Uncle Jokes", he teaches her with Cyborg's help, the art of comedy. When forced to kick her out, he seemed heartbroken-ish.
In BBSFBDAY!, Beast Boy shares his birthday with Starfire after knowing that she has never had one on Earth due to the long Tamaranian years, but later he gets very jealous as she gets most of his gifts. Then they get into a heated argument and this lead to a fierce fight between them because both want to hit the pinata, which Beast Boy wins and takes all the candies, until he realizes he unintentionally injures her feelings and fortunately the two make amends. Beast Boy even transforms himself into a donkey, stuffs himself with candies, and let Starfire hit him so she can experience a pinata. They say "Happy Birthday" to each other and do a birthday dance in the end.
In Brain Percentages, Starfire grieves after Beast Boy calls her the only alien on Earth who tries to make friends desperately and also isolated and sad, she tears up and instantly flies out the dining room.
Blackfire (older sister)
Blackfire is Starfire's older sister, from her home world and birthplace, planet Tamaran. Unlike Starfire, Blackfire is much more cruel and warlike, using any means necessary to benefit herself, even if it means opposing family. She also is the most wanted villain in the universe. Despite her sister's flaws, Starfire has always cared for her, even when her toys were stolen from her as a child.
Starfire loved her as a big sister, and always looked up to her. When Blackfire came to Earth to see her little sister (which turns out she only came to Earth to find Starfire so she could use her as a ploy to escape from the Galactic Police), Starfire was ready on the spot to assist her in anyway possible, and helped defeat the robots that were after Blackfire.
The other Titans were disgusted once Blackfire was introduced to them, knowing better of her real intentions and were wary. Starfire, however, went to bat for her sister and convinced her friends that if Blackfire were to let her down, she would cause destruction on all creatures on the planet. Blackfire then interrupts her sister before Starfire finishes her sentence to her friend, and went on to give her sister a "makeover", to which Starfire happily agreed to. Starfire's clothes were all replaced by Blackfire's attire, and her hair was dyed black to match her older sisters'. The two were nearly identical, and identical enough that the Galactic Police looking for Blackfire, mistook Starfire for her and captured her in her sisters place. While her sister was in jail doing her time, Blackfire felt no remorse initially, and it was only then Starfire's friends said that Starfire is "probably the only person in the universe that loves her". Blackfire realizing this, felt shame for being a terrible sister, and together with the four remaining Titans, helped her become a better sister through training and practice.
Meanwhile, Starfire was in jail, with anger in her eyes, and she vowed to escape jail to pummel her sister into the next dimension for what she did to her. Through intense workouts, Starfire become buff and muscular, completely different from her normal self, and easily broke a hole in jail wall which she used to escape. Once back home at the Titans Tower, Starfire confronted her sister, and was explained in rage how she always used her, and tricked her getting her into trouble. Blackfire apologizes to her, which was not good enough for Starfire, who rushes head on and punches her in the stomach, crashing her through countless buildings and walls that lead far out into the city. Right before Starfire delivers the final blow, Blackfire pulls out a doll she stole from her as a child, and explained she kept it the whole time, and returned it to her and apologized and admitted she has changed now. Starfire, who seemed to be calm from the doll, looked at her sister and said "so have I" with her eyes green ablaze, and disintegrated her own toy, and gave Blackfire a huge blast of a starbolt. The other Titans see poor Blackfire came back to the tower and collapsed, and after Robin asked Starfire about how did she get along with Blackfire, Starfire says "we worked things out" with a smile on her face.
However, in "The Titans Show," things seemed to have turned backwards again for unexplained reasons. Blackfire had covered her body in an aura of lilac-colored fire and converted it into an unusually strong and focused beam of ultraviolet energy, that defeated Starfire easily. She then used her blackbolt eye-beams, in conjunction with See-More and Dr. Light's own beams of pure energy (red for See-More and white for Dr. Light) in an all-out clash against Starfire's own bright green eye-beams. Their combined efforts were too much for Starfire, and she fell backward. She then caught her big sister off guard and blasted her with her eye-beams.
See-More appears to be Starfire rival on the H.I.V.E., as they both possess the same form of attack-eye blasts. The two of them are most frequently shown fighting when the Titans face the H.I.V.E.
In "Opposites", See-More engages Starfire and fires an eye blast at her, but she dodges before chasing him with a starbolt energy blast of her own. She is then showing beating up See-More by punching him in the eye.
In "In and Out", after the Titans reveal themselves, Starfire engages in an eye beam-battle with See-More.
In "Scary Figure Dance", when the Titans turned into ghosts, Starfire possessed See-More and messed around with Raven who possessed Mammoth.
As seen in "The Date", Starfire may had romantic interest in Speedy because she said Robin and him are alike.There is proof of this is when Robin asked her if they could go out, she said: "I would love to, but I can't. Speedy has already asked me." Knowing her personality, she wouldn't care about who asked first, (who was Speedy) and accepted Speedy's invite. In "Starliar", Speedy is somewhat shown to still be interested in Starfire, as he was part of the main group (the Titans East) who invited people to their big annual dance party, and Starfire was the only Titan to originally be invited to the party.
Starfire and Jinx are frenemies. In the episode "Girl's Night Out", Starfire's plan was to free Jinx from prison so she, Raven and Jinx could have a crazy Girls Night Out. When Jinx was freed, Starfire says that if she tries to escape she will blast her into particles as she suspects she will try to run away. Starfire admits that Jinx knows how to bring the fun. She then frees her from the shackles that prevent her from using her powers and enjoys the night with her. When the police catch the girls and are put in the Juvenile Correction Facility, Jinx says that Starfire has even more crazy than her and softens them up after the night out. Starfire then plans to have another Girl's Night Out as she had loads of fun with Jinx. They are friends, but are also enemies by the code.
In "Let's Get Serious", Starfire and Raven are briefly shown freeing Jinx again so they can have their third Girls Night Out.
In "The HIVE Five", Starfire then flies up to Jinx, suspecting she is up to no good. She then spots the black cat, and Starfire and Jinx battle for the cat's love, with Starfire taking the victory. Starfire flies off with the cat in her arms, leaving Jinx alone and angered on the sidewalk.
In "How 'Bout Some Effort", Starfire (along with Raven) willingly tried to cheer Jinx up about her argument with Cyborg.
In Costume Contest, when the Titans and the HIVE are competing with each side for the sake of their desired victory, Starfire and Jinx battle with their reversed powers before colliding with each other.