"Two brothers. One woman. Trouble."In simple terms, a Love Triangle where two of the parties involved are siblings, who both love (or at least try to "get") the third party. This alters the dynamic in various ways, given the famously rather complicated relationships between siblings in the first place. Might go anywhere from a friendly rivalry, one deciding that they want their siblings to be happy or straight into Cain and Abel territory. In Fairy Tales, often inspires the Bride and Switch. If they don't hate each other from the start the Triang Relations version of the triangle is a special subset of #8 or #9. If the former, it will turn into a case of Polyamory. Usually does not involve Brother-Sister Incest. See also Two Guys and a Girl, Sibling Rivalry, and Settle for Sibling. When a fourth party is added in the form of a sibling to the third party, see Double In-Law Marriage.
— Flakita, The X-Files, "El Mundo Gira"
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Anime & Manga
- Pokémon: Diamond and Pearl Adventure! has something similar; both Jun and his father Palmer like Mitsumi.
- Samurai Harem: Asu no Yoichi has a variant of this (Ayame likes Youichi who is kind of a pervert but seems to prefer Ibuki)
- School Rumble has a one-sided variant: Yakumo likes Harima who likes Yakumo's sister Tenma.
- RahXephon has a more serious example with Megumi and Haruka both liking Ayato. Megumi later decides to back off.
- In fact, there's a recursive example (two of the characters are in both love triangles) kinda, sorta with Dr. Kisaragi and Ayato, who are clones, both loving Haruka. At the end, Haruka and Ayato get back together.
- Infinite Ryvius has this as the origin of the Cain and Abel feud of Yuki and Kouji Aiba; they had both fallen for the same woman (implied to be Aoi), and Kouji bows out for both their sakes when he finds out. Yuki takes that as an insult to the woman, and his disgust for his brother lasts for most of the series.
- At one point in the D.N.Angel anime, both Risa and Riku are in love with Niwa. (With the added complication of Dark being in love with... One of them. It's complicated.)
- Chocolat and Tira Misu for Carrot Glace in Sorcerer Hunters. Tira wins in the manga.
- In Spiral, Ayumu was in love with his sister-in-law, and lives with her after his brother disappears.
- In Adachi Mitsuru's Touch, twin brothers Katsuya and Tatsuya both love their childhood friend Minami. Older twin Tatsuya backs off, allowing the younger Kazuya to win at everything, including love seemingly. Then… Kazuya dies in an accident, and the story follows the relationship that develops after this tragedy.
- In Ouran High School Host Club, manga version, both Hikaru and Kaoru are in love with Haruhi. Kaoru backs out because "Hikaru's more important to [him]".
- This also starts off the plot of Judge: Hiro has a secret crush on his friend Hikari, but his older brother Atsuya confessed his own attraction first, so he kept quiet about it. However, at the start of the series, he decides to tell her anyway, and secretly derails the pair's plans to meet for a date, figuring she might be more receptive to his confession if she thought Atsuya had stood her up. Atsuya gets hit by a car because of this.
- Please Twins! plays out like one of these. The plot consists out of two girls that turn up at a boy's house claiming to be his twin sister. The boy and the girls need to find out who is the real twin sister while falling in love with each other.
- Simoun has an unusual example: a Type 5 triangle where Alti loves her older sister Kaimu who crushes on Paraietta who doesn't have feelings for any of them (because she's in love with Neviril).
- Wandering Son initially had a Love Triangle between two siblings. In middle school Maho fell for a boy named Riku, so she asked her transsexual sister Nitori to dress up as a girl after Riku had fallen for her. Even after he finds out Nitori's sex he seems to be somewhat attracted to Nitori. It eventually faded though and he and Maho became a happy couple who are still together even at the end, when Nitoro goes off to college. It's never quite said whether Nitori herself had feelings for Riku, but she later gets a girlfriend.
- Brother-Sister Incest version in shojo manga Vampire Knight with both Kuran brothers, Rido and Haruka, in love with younger sister Juri. (Marriage between siblings is common among pureblood vampires however). And Juri chooses Haruka anyway. Which later means trouble for Juri and Haruka's daughter Yuuki, since Rido reappears and becomes fixated on her.
- In Star Driver pink-haired twin sisters Mizuno and Marino You both fall for the same boy, male lead Takuto Tsunashi. It is later revealed that Marino is in fact a clone created by Mizuno's first phase power, which may account for them both liking 'the same things.'
- A variation of this can be found in The World God Only Knows, with the Jupiter Sisters, who possess the bodies of girls belonging to Keima's Unwanted Harem. Somewhat subverted later on, after one of them revealed that they're not actually related and the "Jupiter Sisters" is a collective title bestowed to six priestesses whose powers complement each other to a devastating synergistic effect. They truly regard of each other as sisters, though.
- Koki, Tanpopo, and Yoji in Imadoki! It's more one-sided on Tanpopo's end, as she and Koki very clearly have feelings for each other, but when Yoji confesses his own feelings for Tanpopo, she briefly dates him.
- Shinshi Doumei Cross has Shizumasa and Takanari, both in love with main heroine Haine.
- Claudine has two. Both of the Lacques siblings (Louis and Cecilia) were lovers to the main character's father Auguste, and later both Claudine and his elder brother Andre fall for the same girl, Sirene. Both cases end up in death and tears.
- Played with in Anatolia Story. Yuri's twin caretakers Ryuhi and Shala have the same taste in men, thus they fall for Kail's advisor Kikkuri and visit him at night, with Kikkuri not realizing that he's sleeping with them both since he can't distinguish them. When the girls get pregnant at the same time and the deal is revealed… Kikkuri marries them both, and the seven members of their little family (since both girls gave birth to twins) live happily from then on.
- And one of the guys who loves Yuri is Prince Zannanza, who also happens to be one of Kail's half-brothers.
- Happens in Yoko Hanabusa's Lady, with the Russell half-sisters Sarah and Lynn having feelings for Arthur Brighton. Sarah and Arthur get together, while Lynn's feelings shift towards Arthur's younger brother Edward.
- In Revolutionary Girl Utena, both Anthy and her brother Akio manage to bed Utena and each other (not very willingly from Anthy's side, tho). A type 8 Triang Relations with some positively disturbing sex scenes. Nanami finds out and is traumatized by the knowledge, so she tries to warn Utena to no avail.
- In The King of Fighters Radio Drama The Sun and the Moon, Iori Yagami finds himself in a triangle with his two Morality Pets, the sisters Konoe and Kikuri Tanima. He ends up with… neither of them: he leaves Japan to protect them from himself, and Kikuri dies of illness later.
- The Vampire Princess Miyu manga gives us Kyo Kitami and the Minami sisters, Mari and Rima. The guy is fascinated with the older sister Rima who is actually a cute mermaid kept in a tank, while the younger sister Mari is tasked with luring Kyo so their Shinma dad can drink his blood, but ends up falling for him…
- Fullmetal Alchemist:
- Apparently, Ed and Al used to have this in their childhood, fighting over who would marry their friend Winry, who wasn't interested in either of them. Eventually, Winry did develop a thing for Ed and Ed returned her feelings; Al aknowledged this and went the Shipper on Deck way without any problems.
- In the first anime, Scar was in love with his older brother's girlfriend. She later died and Scar's brother fell enough into despair to try Human Transmutation to bring her back, before his own death... unwittingly creating the homunculus Lust in the process. The brother's Famous Last Words are basically a mix of an apology to Scar ("I'm sorry, you probably deserved her more") and a reaffirmation of his feelings ("But will see her first").
- Kimi ni Todoke has a variation: Ryu is a Patient Childhood Love Interest to Chizuru, who has a crush on his older brother, Toru.
- Sakura Trick: Haruka has the affections of both Sonoda sisters. Since her relationship with the younger one is the entire basis of the series, it's easy to guess how things will turn.
- A good portion of Princess Jellyfish's plot revolves around two brothers both liking the same woman, one being a Wholesome Crossdresser and the other not even realizing the woman is the same person as the geeky, meganekko he hates.
- Free! sorta takes this direction in the second season, with both Mikoshiba brothers (eldest Seijuuro and youngest Momotarou) crushing on Gou Matsuoka. She doesn't seem to be aware of it.
- Tengen Toppa Gurren Lagann, kind of—Simon and Kamina aren't brothers in the biological sense, but always refer to themselves that way and consider themselves as such anyway. Simon initially has a Precocious Crush on Yoko, and gets a hard kick in the heart when he sees her and Kamina having their First Kiss. Romance between him and Yoko more or less vanishes after that, though, even with Kamina dying that same episode. note . Anyway, the trope soon becomes moot since Simon soon meets Nia and falls for her…
- Averted in Fushigi Yuugi Genbu Kaiden. Both of the Urumiya twins, Hagas and Tegu, fall for Princess Firuka… but at different times. Hagas, who loved Firuka because she helped him live a little longer, dies in a Self-Sacrifice Scheme to release Tegu from Firuka's Archnemesis Dad and give him the title of "Urumiya" Senshi; Firuka meets the now free Tegu, he tells her how much Hagas loved her even when he couldn't show it, and later they get married.
- The biggest example in Futakoi is the love triangle between protagonist Nozomu and the Ichijou twins; Kaoruko and Sumireko. The twins both love Nozomu and this causes a bit of tension between the twins.
- In Macross Zero, sisters Sara and Mao Nome both end up falling in love with Shin Kudo. Mao is more openly affectionate, while Sara's feelings are more conflicted due to Shin being an outsider.
- A variation occurs in one of the The Legend of Zelda manga based off of Zelda II: The Adventure of Link. The current Zelda and the recently-revived Sleeping Zelda both fight over Link at the end. They're distant relatives as the latter had been comatose for centuries, and the current Zelda is presumably a descendant of her brother.
- Kyou Kara Yonshimai has Sakura's friend falling for her. He later meets her older sister and is attracted to her until learning that she is the "brother" he called gross and obnoxious for living as a woman. Kashiwa finds him annoying for harrassing her sister and is uninterested in him (plus she has a girlfriend anyway).
- In the Child Ballad The Twa Sisters, the sister's motive in drowning her sister is jealousy.
- In Ultimate X-Men, Lorna (aka Polaris) dated Scott (aka Cyclops) in the backstory, and his brother Alex (aka Havok) in the series' present.
- In the normal X-Men continuity the Summers brothers had another one: Madelyn was married to Scott and later fell for Alex. Furthermore Scott had left her for Jean, whom it turned out Madelyn was a clone of, so… maybe this works both ways?
- In Buffy the Vampire Slayer Season Eight, Buffy realizes that she may have romantic feelings for long-time platonic friend Xander. She goes to tell him, only to discover that he has just started a relationship with her sister, Dawn. (This is all made even more complicated when you remember that Xander had a crush on Buffy in season one and Dawn had a Precocious Crush on Xander in season five).
- In one Batman Black and White animated comic "Two of a Kind", Harvey Dent is rehabilitated by a combination of therapy, plastic surgery, and a romance with the plastic surgeon. Said plastic surgeon has a twin sister who is immediately smitten with Harvey because she is even crazier than Two-Face and believes they are two of a kind. She tempts Harvey into cheating on his fiance, but he eventually breaks it off with her. It ends in tears just as all of Harvey's attempts to be free of Two-Face do.
- Issue #9 of My Little Pony: Friends Forever involves the identical twin unicorn Con Artists Flim and Flam having broken up over their mutual attraction to a librarian named Marian. Granny Smith gets them back together by revealing she was the non-sibling member of one of these herself in her younger days, with the "Jonagold Brothers" never speaking to each other for the rest of their lives after she backed out of their feuding over her.
- Cinderella's stepsisters have been known to cut off parts of their feet to fit in the shoe.
- In "The Wonderful Birch", the witch made the items fit her daughter; her stepdaughter let the prince know the truth and so they used the witch's daughter to make a magical bridge and he married the stepdaughter; the witch then replaced the stepdaughter with her daughter after childbirth.
- In "The White Bride and the Black One", the stepmother murders her stepdaughter en route to the wedding and substitutes her own daughter.
- In the Chinese tale "Beauty and Pockface", Pockface takes Beauty's place after she visited her family, and weeps and wails about how he never really loved her because he no longer does after she contracted smallpox.
- In "Fair, Brown, and Trembling", Trembling goes to church, and a prince falls in love with her, and out of love with Fair. After she has a baby, Fair pushes Trembling into the sea and takes her place.
- In "Tsarevitch Ivan, the Fire Bird and the Gray Wolf", after they murder Ivan, his brother draw lots about who gets to marry Helen the Beautiful.
- In "The Story of Tam and Cam", Tam is murdered by her stepmother, who gets the king to marry Cam in her place, but Tam keepts coming back.
- In "The Golden Bird", the brothers try to murder their younger brother and keep the beautiful maiden.
- In "The Water of Life", the older brothers try to woo the princess who had agreed to marry their younger brother.
- Averted in "Snow-White and Rose-Red": it turns out that the prince whom they free from an evil dwarf's spell has a younger brother at home. Snow-White marries the elder prince and Rose-Red gets together with the younger.
Films — Animation
- Strange Magic: Princess Dawn is accidentally love potioned into loving The Bog King who views it as an annoyance. Later, her sister Marianne breaks in to rescue her. She and the Bog King begin to fall in love over their shared loved of fighting. Dawn is broken out of the love potion when she has a Love Epiphany for someone else, ending the triangle without acrimony.
Films — Live-Action
- Duel In The Sun was largely about this.
- In the film The Man in the Moon, Emily Warfield and a very young Reese Witherspoon are sisters both in love with Jason London. He dies, forcing the sisters to reconcile.
- Before The Devil Knows You're Dead
- The Patrick Dempsey film Some Girls has a young Dempsey falling for three sisters, although he sleeps with only one and in the end doesn't wind up with any of them.
- The Emperor murdered his brother and married his brother's wife in Legend of the Black Scorpion. Wan didn't want anything to do with this, but she submits. Or appears to.
- Implied in The Lone Ranger with Dan and John with Rebecca before John left to learn law. Dan married Rebecca and have a son, Danny Reid (Jr.). It is implied that Dan knows John and Rebecca still loves each other.
- Linda and Julia Seton get into one when Linda falls in love with Julia's fiancé Johnny in Holiday. Linda, who loves her sister, staunchly refuses to act on her feelings until the end of the movie.
- Silent comedy film Hands Up! features the protagonist falling in love with each of a pair of sisters. He resolves this dilemma by—marrying both of them.
- In I Wake Up Screaming, Frankie the promoter takes an interest in Vicki, plucks her from waiting tables, and makes her a famous model—but winds up falling in love with her sister Jill, much to Vicki's displeasure.
- Dan in Real Life; the titular character meets a woman at a bookstore and they hit it off. A few minutes later, he finds out the woman is his brother's new girlfriend.
- Somewhat odd version in While You Were Sleeping. Lucy has a crush on Peter, and when he winds up in a coma due to an accident, his relatives misunderstand the situation and think she's his fiancee. His brother Jack is very attracted to Lucy. When Peter comes to, he thinks he's lost some memories of Lucy, but is game to give a relationship with her a chance. Meanwhile, Lucy's finding out that she's attracted to Jack. She winds up with Jack, and all parties consider this for the best.
- In Atlantic City, Sally's husband Dave shows up in Atlantic City with Sally's sister Chrissie, whom Sally has impregnated, in tow. Sally is super-pissed about this.
- North Sea Texas gives a non-heterosexual example. Siblings Sabrina and Gino are attracted to Pim, who returns feelings for the latter.
- In The Patsy, Pat is besotted with her sister Grace's boyfriend Tony. Tony has no clue. Grace for her part is also attracted to another man, complicating the situation.
- In the Warhammer novel Defenders of Ultuahan two brothers love the same woman. One brother leaves the other brother to die during a skirmish. This comes back to bite him in the arse.
- In Harry Harrison's The Stainless Steel Rat Goes to Hell Digriz' two twins fall in love with the same woman. The problem is solved by going to a parallel universe and fetching an alternate version of said woman.
- Casson Family Series: Bill cheated on his wife Eve with Eve's twin sister Linda. He knew her first, so Eve didn't even really mind.
- Sandy and Dennys in Many Waters both love Yalith and she loves them both back. Unfortunately, the relationship as such is doomed because the flood's coming and Yalith isn't allowed on Noah's ark.
- Played with darkly in Hellraiser: Julia has married Larry, but eventually murders him in preference for his brother Frank, who seduced her prior to the events of the film. It doesn't really go well for her....
- The Bible has a rather complicated example with Jacob, Rachel and Leah. Jacob fell madly in love with Rachel, and worked for her father/his uncle Laban for seven years in order to earn the right to marry her. However, in Rachel's society it was shameful for the younger daughter to be married first, so (with some help from the very thick veils used at the time, as well as some alchohol) Laban switched Rachel out with Leah, with Jacob only finding out during the wedding night. Rachel and Laban then forced Jacob to work another seven years so he could marry Rachel for real. One can't help but wonder what poor Leah felt about this arrangement. (In a slightly unrelated note, this is why we have the tradition of the bride removing her veil in Western weddings.)
- For an added complication, a Jewish legend says that Leah was originally destined to marry Jacob's older brother, Esau, who was far less meritorious; Leah was overwrought and prayed to God, who then arranged things so she could marry Jacob as well.
- And, to make things even more complicated, two handmaidens were involved. Who in some legends were also Leah and Rachel's sisters.
- In the biblical fiction book The Red Tent, about Jacob and Leah's daughter Dinah, this is one of the main plot points. Jacob loves Rachel but also loves Leah. This is further complicated by the book saying that the handmaidens (Bilhah and Zilpah) are their sisters. Which is true in some Jewish lore as well.
- For an added complication, a Jewish legend says that Leah was originally destined to marry Jacob's older brother, Esau, who was far less meritorious; Leah was overwrought and prayed to God, who then arranged things so she could marry Jacob as well.
- In the Isaac Asimov short story To Your Health, two brother opticians are in love with the same eye-fixated girl.
- Mansfield Park: The Bertram sisters go after Henry Crawford (despite Maria Bertram already being engaged). The results: Crawford plays with their hearts for his own amusement until their Disappeared Dad returns home, goes after their cousin Fanny next because she's the only girl on the planet immune to his charms, and runs away with Maria after she's already married.
- All over the place in The Demon's Lexicon.
- Before the start of the series, Nick and Sin had a casual relationship that he ended. In the beginning of the third book Nick seems to enjoy Sin's company and his brother Alan bribes her to spend time with Nick. The 'triangle' bit kicks in when Sin and Alan begin to fall for each other and ultimately become a couple.
- Spanning all three books is the one Nick and Alan have with Mae. They're both attracted to her and she's attracted to both of them.
- Mae gets another one with Seb and her brother Jamie. She briefly dates Seb before finding out that he's gay, in love with Jamie, and using her as The Beard and excuse to be around him. Jamie dislikes Mae dating Seb because Seb bullied Jamie and mocked Jamie for staring at him when they first met. This prevented their classmates from becoming suspicious of Seb's own sexuality and effectively ruined Jamie's social life. Jamie resented Seb for that, but still winds up with him in the end.
- A dark version in the backstory to The Elfstones of Shannara. The Witch Sisters, Morag & Mallenroh, both fell in love with a human. Given that they're a pair of Selfish Evil Yandere sociopaths, this ended with him dead, and each of them blaming the other one.
- East of Eden (which is, after all, based on The Bible), has two of these. Cathy marries Adam after sleeping with his brother Charles. Later, Cathy's sons Cal and Aron like the same girl, Abra. She's interested in Aron when they're children, but their relationship becomes strained in high school, and she switches to Cal toward the end of the book.
- In the backstory of Eight Cousins, a woman named Rose was courted by the brothers George and Alec Campbell. She chose George and married him, but at the cost of the distancement between George and and Alec. Sadly, Rose died early in her life, and some years later George perished as well; in George's deathbed, the brothers were reconciled, and Alec promised the dying George to take care of his and Rose's daughter, Rose Jr. aka the female lead of the story.
- In One Hundred Years of Solitude, Hookerwith A Heart Of Gold Petra Cotes regularly sleeps with the twins Jose Arcadio Segundo and Aureliano Segundo without realizing they're not the same dude. The three contract a STD, which reveals the whole deal, and she breaks up with them. Jose Arcadio Segundo leaves Petra after getting better, but Aureliano Segundo gets her forgiveness and keeps her as The Mistress since he cannot marry her.
- In the Lowlands Of Scotland series, sisters Rose and Leona both fall for their cousin Jamie after he arrives at their father's home. However, Jamie only has eyes for Rose, until he accidentally ends up married to Leona and learns to love her. And then when Rose's machinations work and he is broken up from Leona and married to Rose, he has to learn to love Rose all over again. And the sisters have to work through both of them loving and having been married to the same man.
- Actually averted in Little Women. Laurie only fell for Jo's younger sister Amy after being rejected at least twice by Jo herself, and later they both see they're much better in a Like Brother and Sister relationship. The fandom still acts as if Amy was a slut who deliberately stole "Jo's True Love".
- Also averted in Eva Luna. Rolf Carle is smitten with both of his cute cousins and cannot decide who to choose since both girls are appealing to him in their own ways. The girls talk about this and they decide to... share his body and affection and tackle him together when he's working in the garden. They keep this relationship for several years, until the girls marry local guys and Rolf becomes an Intrepid Reporter; nevertheless, they always remember these times very fondly.
- Played with in The Infernal Devices. Though the main character, Tessa's, love interests are not biological brothers, they are parabati, which for Shadowhunters is quite close to being brothers. There isn't a 'Mundane' equivalent for it.
- In the backstory of A Song of Ice and Fire, in accordance with Valyrian tradition, Aegon Targaryen (later known as Aegon the Conqueror) was required by his parents to marry his older sister Visenya, but he was in love with his younger sister Rhaenys. His solution was to marry both of them, which was unusual, but allowed. Understandably, Visenya was not happy about having to share a husband with her sister, especially since Aegon favoured Rhaenys and named their son Aenys as his heir instead of Visenya's son Maegor, who was much more martial and warrior-like. Even after her sister's death, she still hated Rhaenys and blamed her for Aegon wanting nothing to do with her. She got her revenge (sort-of) long after her siblings' deaths, when she poisoned her stepson/nephew when he sought refuge with her and installed Maegor on the throne after Aenys's death. Eventually she lost out when Maegor died without issue and the throne passed to Rhaenys' son Jaehaerys, and all Targaryen kings since then were descended from Rhaenys.
- Chloe from Darkest Powers is stuck between a love triangle involving the foster brothers Derek and Simon. She chooses Derek.
- In The Stainless Steel Rat, Jim's twin sons James and Bolivar fall for the same young female agent. And she falls for both of them too, unable to decide between them. Fortunately, the triangle is resolved by the discovery of an alternate universe, which seems to double any signal sent to it, which includes physical objects. The woman ends up not only twinning herself, but the two identical copies share a Hive Mind. In later books, this serves as a useful method of instantaneous communication across light years.
- Arrested Development played with this. Michael develops feelings for Marta who is with GOB. GOB is mostly using her but he doesn't want Michael to have her either. Also Buster has a crush on Marta. All three of them are rebuffed by Marta eventually.
- Later there's a Running Gag of GOB trying to seduce women that Michael likes, but repeatedly getting the wrong woman. (For instance, when Michael is dating his son's ethics teacher, GOB ends up seducing a different teacher by mistake.)
- Tommy and Justin of Brothers and Sisters were both dating Lena, though not precisely at the same time.
- An episode of Little House on the Prairie has Laura with a crush on an older boy, who has a crush on Mary (Laura's older sister).
- Wizards of Waverly Place: Due to Tutor's being part elf, Justin and Alex fight over her like this. While Alex's fighting for her is supposed to be platonic it has been taken in other ways.
- In the British thriller series The Last Enemy, Stephen and Yasim start a relationship with each other after her husband (his brother) dies in a car bomb. Then the brother comes back.
- The Vampire Diaries brings us Damon and Stefan Salvatore who became vampires after falling in love with Katherine, a vampire that abuses their love triangle. After she is seemingly killed the brothers eventually end up in Mystic Falls where they both fall in love with Elena, who looks exactly like Katherine.
- And in the past, Klaus and Elijah over Katherine.
- Klaus reveals that he and Elijah fell in love with the same girl - Elena and Katherine's ultimate ancestor - when they were still human. It was her blood that they unknowingly consumed when their mother turned them into vampires, which explains the need for the doppelganger. (Katherine is the first doppelganger and Elena is the second).
- While they aren't siblings Elena/Stefan/Katherine kinda counts considering that Katherine is Elena's great-something grandmother. Try not to think about that one too hard.
- One episode of The Secret World of Alex Mack has Alex get a crush on a boy, who she later finds out is dating her sister. She tries to keep him from breaking up with Annie, and when he does anyway, she refuses to date him because he dumped her sister for her.
- Probably happened more than once on Degrassi: The Next Generation, but Adam and his brother Drew fought over Fiona, before Drew bowed out.
- A weirder example is the Declan/Holly J/Fiona triangle. Because they moved around a lot Declan and Fiona were very close but after Declan fell for Holly J, Fiona did everything she could to try to drive Holly J away including kissing her brother at a party. After getting therapy, Fiona became good friends with Holly J eventually realized she’s a lesbian and was in love with Holly J.
- One episode of Roseanne has Mark almost take a girl out on a date just because his younger brother David wanted to. His Jerk Ass-ery is repaid when his wife almost finds out, and David, after helping him hide it from her, asks Mark if he really wants to go out of his way to alienate the only two people who really care about him.
- One episode of Sister Sister has a guy accidentally ask identical twins Tia and Tamara out on a date because he couldn't tell them apart. The three go on a rather awkward date together when he comes over and the mistake is realized. Both also liked Roger after he suddenly becomes hotter, and he winds up dating each of them at some point.
- In an episode of Frasier, Frasier and Niles think they're participating in this trope as they compete for the affections of a certain woman at a party, but they realize they've been talking about two different women all night...right after they decide their sibling bond is more important than a random woman, let the object(s) of their affections leave the party without propositioning them. Cue double Oh Crap! expressions.
- In The Borgias, thirteen-year-old Joffre Borgia marries Femme Fatale Sancia, who has a torrid affair with his elder brother Juan. Incidentally, Juan was supposed to be the one marrying Sancia in the first place but he refused on the grounds that she's a mere Royal Bastard, (despite the fact that he's infamously illigitimate himself what with being the son of the Pope and all) but he doesn't mind having sex with her literally seconds before she consummates her marriage with poor Joffre. Also, while the show hasn't had time to portray this yet, historically Sancia later had an affair with the eldest Borgia sibling Cesare, making it a sibling love square (this situation is sometimes cited as the reason for Juan's eventual murder at the hand of Cesare.) Yeah. The term Big Screwed-Up Family barely even covers it. Particularly when you factor in the various Sibling Triangles engendered by Cesare and Lucrezia’s incestuous relationship (whether the show will actually go there remains to be seen, but so far the Incest Subtext is hardly subtle). Cesare threatened to murder her first husband Giovanni if he ever hurt her, and he allegedly DID murder her second husband Alfonso (Sancia’s brother) purely out of jealousy.
- Wataru, Taiga and Mio in Kamen Rider Kiva, though Wataru and Taiga initially do not know they are brothers.
- On Murdoch Mysteries, Detective William Murdoch and Dr. Julia Ogden have the cutest Will They or Won't They? tension. In the episode "Houdini Whodunit", Julia's younger sister Rugy appears and flirts with Murdoch immensely daringly, and even invites him for romantic dinner, which is quite a big deal for the Victorian times. However, Julia doesn't give up: When she comes to the restaurant to discuss the case (originally unaware that they are there together), she seems hurt by seeing them, but she ultimately decides to join them and fight. Understandably, Ruby is irritated, but when she sees how serious Julia is about the Detective, she starts supporting her and becomes their Shipper on Deck.
- On Grimm, the Renard half-brothers have both had involvements with Adalind and it's currently uncertain which, if either, is the father of her unborn child. She may not even be all that sure about that point herself.
- The Brady Bunch episode "Cyrano de Brady" has Peter pining for a friend of Jan's and asks for Greg's help in wooing her. Unfortunately, the girl thinks it's the other way around and throws herself at Greg, pissing Peter off and leaving Greg with an unwanted admirer. Fortunately the triangle works in Peter's favor in the end.
- A smaller one occurs in "The Not-So-Ugly Duckling", when a boy Jan likes drools over Marcia. However, Marcia has zero interest in the boy, despite Jan's accusations of boyfriend-stealing.
- In Helix, Julia, a CDC researcher, became unhappy in her marriage to coworker Alan and turned to his younger brother Peter, a research scientist, for comfort. After Alan caught them in bed together, Julia divorced Alan and totally cut off contact with Peter. In the present, both brothers carry a torch for Julia, while Julia struggles with unhappy memories of her marriage to Alan and still-present feelings for Peter, all in the midst of an outbreak of The Virus at a Research, Inc., which Alan and Julia have been sent to contain, with Peter as the Patient Zero.
- Arrow has the Lance sisters, Sarah and Laurel who competed, rather bitterly, for Olliver's affections. Sara being on the boat with Olliver has shades of revenge and spite for Laurel.
- In the CSI episode "Exile", two sisters loved the same man who had been a childhood friend, but he only reciprocated the feelings of one. The episode begins with one sister's body being discovered and it goes downhill from there.
- One episode of Living Single had Regine seeing both an older gentleman and his son, Played by real-life father-son duo Melvin and Mario Van Peebles.
- In the fourth season of Falling Skies, Ben falls for his older brother's girlfriend Maggie. It blossoms into a full-fledged love triangle when some of Ben's spikes are transplanted to Maggie in a last-ditch effort to save her life, creating a connection between the two of them.
- During the mid-90's on General Hospital, both AJ and Jason Quartermaine fell in Love at First Sight with Keesha Ward, with Jason being the one lucky enough to snag her. This didn't stop AJ from continuing to lust after Keesha and trying to find ways to undermine the relationship.
- Also frequently done on The Bold and the Beautiful—Ridge and Thorne battled over Caroline and later Taylor, Brooke and Katie battled over Bill. In fact, there's too many Soap Opera examples to cite.
- Played With in Supergirl—teenage Carter has a Precocious Crush on Supergirl while his older half-brother, Adam, briefly dates Kara.
- In One Tree Hill, Lucas and Nathan Scott both want to date Peyton throughout a large portion of the first season. However, it is not treated as a sibling-triangle in-universe, because the two are half-brothers who were not raised together and spend much of the same arc as rivals. When the two finally decide to become friends and acknowledge each other at brothers, they also stop competing for the same girl with Lucas dating Peyton and Nathan dating Haley.
- Played with on the Buffy the Vampire Slayer episode Him. Dawn falls for this guy (or accurately, his love-spell inducing letter jacket). Then Buffy falls under his spell. They fight over him. A lot. And then the triangle expands into a pentagon, when both Anya and Willow (despite being a lesbian and all that) fall for the spell too.
- Played for Laughs in NCIS: Los Angeles when Kensi sabotages Deeks' attempt to use her as his unwilling wingman to pick up some women exercising in a park. She yells at him that she's not leaving him because of his job (as he claims), she's leaving him because he cheated on her with her brother.
- In the folk song "William and Davy", twins William and Davy fight bitterly over the woman they're both in love with... who, as it turns out, isn't interested in either of them.
- On WWE Smackdown, Primo Colon started dating the "mysterious" Brie Bella, only for her to reject him out of the blue and start showing interest in his brother Carlito. Victoria and Natalya would expose Brie's hidden twin sister, explaining this erratic behavior. Rather than get angry, the brothers ended up going on double dates with the sisters.
- At the end of November 2010, both of Bella Twins started going after Daniel Bryan in WWE Raw, with this trope being the inevitable result.
- This forms a large part of Strahd von Zarovich's backstory in the Ravenloft setting of Dungeons & Dragons, and recounted in the book I, Strahd. He and his brother Sergei both ended up falling for a woman named Tatyana, but Tatyana chose the younger Sergei and Strahd decided to make a literal Deal with the Devil in exchange for restored youth and power and killed Sergei himself on the day of his wedding to Tatyana. When he tried to woo Tatyana, however, she again rejected him and threw herself from the top of Castle Ravenloft to her death.
- Verdi's Il Trovatore. And the boys don't even know they're brothers. Consequence? Well, it's an opera...
- Other operatic examples include Pelléas et Mélisande by Debussy (based on Maeterlink's play), and Amadis by Jules Massenet.
- A variation exists in The Love of the Nightingale. Tereus has an Arranged Marriage to Procne but falls for her sister Philomele. However neither even likes him.
- This is basically the plot of "The Bartered Bride", the opera by Bedrich Smetana. Marenka and Jenik want to get married, but Marenka's parents have already employed a matchmaker to hook her up with the son of a rich man named Micha. The matchmaker demands Jenik break up with Marenka, and Jenik promises he will do so if the matchmaker pays him off and promises that Marenka won't marry anyone else but Micha's son. Jenik, of course, turns out to be Micha's long-lost son, and he and Marenka get married.
- A major plot point in Blood Brothers is both Mickey and Eddie being in love with Linda. However none of the three know that Mickey and Eddie are brothers.
- In Hamlet, Claudius murders his brother Hamlet Sr. and marries his brother's wife Gertrude a month later. It's heavily implied that she herself was in on the plot.
- Les Jumeaux de la Réole, a play about twin French generals César and Constantin Faucher, briefly features this: César is in love with Eudoxie, their colonel's younger sister, and she is in love with Constantin. In the end, it is César who marries Eudoxie.
- In Hamilton, sisters Angelica and Eliza are both in love with Alexander, but Angelica puts her romantic feelings aside because she cares about her sister's happiness above all else.
- Beethoven, CB, and CB's sister in Dog Sees God.
- In the Warcraft universe, Night Elf brothers Malfurion and Illidan Stormrage both vie for Tyrande Whisperwind's affections. Illidan's rage and jealousy towards Malfurion for so effortlessly (and unintentionally) winning Tyrande's affections played a large part in triggering Illidan's Face–Heel Turn.
- And in Frozen Throne it's revealed that he still cares for her; the news of her being dead (not really) triggers a Heel–Face Turn where Illidan fetches her, gives her back to Malfurion then leaves their lives for good.
- In Diablo III Lyndon the Scoundrel and his brother Edlin both fell in love with a woman named Rea. Rea eventually chose Edlin, who was himself unaware of Lyndon's love for her. The relationship was further complicated when Edlin botched his the scam he was running with Lyndon and ended up in jail, after which Rea became convinced Lyndon had set it up to get her.
- In Persona 2: Eternal Punishment, Tatsuya and Katsuya are both in love with Maya. Katsuya's Shadow taunts him with this and uses it to try to get him to shoot Tatsuya. Katsuya says that while the Shadow is right about his feelings, he loves his brother anyway, and shoots the Shadow instead.
- In Dragon Age II, Hawke's younger brother Carver cautiously tries to win the affection of Merrill, one of Hawke's possible love interests. He does not succeed, as Merrill seemingly doesn't notice, but if Hawke and Merrill become a couple, in a later Party Banter Carver bitterly comments "So, you and Merrill.", to which an aggressive Hawke replies "Yes. I and Merrill". A similar situation can arise regarding Hawke's sister Bethany and Sebastian, but it is less severe, as Bethany and Sebastian don't spend much time in the party together.
- Also implied that Merrill knows exactly where Carver's trying to go, but is feigning obliviousness to let him down gently, since she's got a massive crush on Hawke.
- Carver also shares a mutual attraction with Isabela, which leads to a funny reaction from Hawke when Isabela gets turned on by Carver's flirtation.
- In the backstory of Symphonic Rain, both Arietta and Torta Fine were in love with Chris and despite everyone saying Torta complimented him, he ended up getting together with Arietta.
- In Taketo's route of Class Trip Crush, Taketo and the protagonist are well on their way to falling for one another when the protagonist finds herself hitting it off with Taketo's twin brother Yasuto... who quickly starts to fall for her as well. Confusion, awkwardness, and hurt feelings soon abound.
- In the original Double Dragon, Jimmy Lee is in love with brother's girlfriend, Marian, who gets kidnapped by the Black Warriors. If two players defeat the final boss together, Billy will challenge Jimmy over Marian.
- In Beyond the Horizon Ruth, who was betrothed to Andrew, picks his brother Robert instead. All three live to regret it, as Ruth realizes pretty soon that she actually did love Andrew, and her marriage to Robert descends into hatred and bitterness.
- In Shall We Date?: My Sweet Prince, the heroine has to choose which brother she thinks is fit to be king. And she has to choose among six brothers. Cue wacky hijinks and Sibling Rivalry, especially between Alvah and Jun.
- The twins Ryou and Kyou in CLANNAD both like Tomoya, who is friends with Kyou but barely knows Ryou. Seeing that she can't get close to him on her own, she enlists her sister knowing how she feels. After a brief fuss, Tomoya agrees to go out with her, only to realize a week later that he doesn't actually like her and probably never will. He manages to deny it to himself for awhile but after awhile it just becomes impossible and he admits that he likes Kyou. Ryou, knowing the score, desperately tries to cling on to him by acting more like her sister. She can't do it because this is the Kyou route. You can get a Ryou ending by making the wrong choices, but you don't get a proper ending and the relationship is just as shallow and unlikely to last as it is in the Kyou route.
- The twins Itsuki and Sayo both fall in love with Akira in Suika. It ends when right before Akira has to move away, they have a fight over who gets to give him the present they made for him. Itsuki pushes Sayo down the stairs and thinks she's killed her, before REALLY getting killed by her insane father. The Itsuki we meet later is actually Dead All Along, while Sayo is hospitalised and in a coma.
- In Under The Moon, twin brothers (of course twins) Leni and Seizh are both madly in love with the heroine, Ashe. Emphasis on the "mad" part. There's a distinct possibility that they'll kill each other over her.
- In Higurashi: When They Cry, At first Shion seems to like the same boy as her identical twin sister Mion, but she subverts it since it's later shown she was simply teasing and is actually in love with Satoko's brother Satoshi, who disappeared under mysterious circumstances. Depending on the route, sometimes she encourages Keiichi and Mion to get together, and sometimes she sabotages their relationship out of jealousy. Like everyone in that story, she has issues.
- In Tsukihime the Meido twins Kohaku and Hisui are both potential love interests for the main character Shiki, but on different routes. A key part of their story involves the fact that they both knew Shiki when he was a kid, but Shiki doesn't realize the two pulled a Twin Switch and that the Genki Girl was really Hisui while the sad girl in the window was Kohaku, the opposite of their current dispositions.
- In Liar Liar it's revealed that Yukari is out to kill her (technically ex) boyfriend because he confessed to her little sister Minami. He ended up two-timing them before breaking up with Yukari to be with Minami.
- Da-Jeong in The Friendly Winter has feelings for a local boy who doesn't like her back, or even know that she's nineteen, not nine. It turns out he has a girlfriend—who is unknowingly her younger step-sister on her mother's side. Da-Jeong's mother walked out on her family ten years ago, due to her daughter's disorder, and they haven't seen each other since.
- Spoofed by YouTube contributor Ben Loka in his video "Never Trust A Sat Nav". After his argument with the Sat-Nav turns into a lover's spat, Ben reveals he's cheating on it with someone the Sat-Nav identifies as her sister: a road atlas.
- Semi-example: In one episode of Teenage Mutant Ninja Turtles, three of the four Turtles eat pizza tainted with a love potion, causing those three to fall in love with Irma. Hilarity and in-fighting ensue, until Splinter and the unaffected Turtle, Donatello, find a way to counteract the potion. Afterwards, further hilarity ensues when Irma discovers who was actually courting her.
- Played for Laughs on Phineas and Ferb, when Candace's Kid from the Future refers to Isabella as her aunt.
Isabella: 'Aunt Isabella!' That means I'm going to marry Phineas!Candace: Or Ferb.
- In one episode of Ugly Americans, Callie gets a little sister, Lillith, who plans to kill Callie and have sex with her boyfriend, Mark, most likely against his will. Made even weirder because Mark and Callie had raised her since she was a toddler (two weeks before).
- ThunderCats (2011) establishes a triangle between adoptive siblings Lion-O and Tygra and their bodyguard/priest Cheetara, with Cheetara unaware that the brothers are jockeying for her favor behind her back. It's later revealed that Tygra and Cheetara were friends as kids, which is why Tygra took an interest in her Cheetara ends up choosing Tygra — and in fact she had loved him for a while already, only that her duty was her first priority..
- In The Legend of Korra, Bolin has a crush on Korra, while she has a crush on his older brother Mako, who likes her back but has trouble admitting it. For added confusion, Mako is dating another character, Asami. Ultimately ends with Mako and Korra hooking up.
- Happens in Gargoyles, though this is an odd example since all gargoyles of the same clan and generation consider themselves siblings. Still, "Othello" and "Iago" refer to each other this way as they fight over the former's mate, and all three members of the Trio compete over Angela when she first arrives.
- On Daria both of Sandi's younger brothers have Precocious Crushes on Quinn.