Triang Relations - Television Tropes & Idioms

alt title(s): Triangle Relations

The first assumption in a relationship described as a Love Triangle is that someone has got to go. Lots of good drama/comedy in that little conundrum.

Even if the writer chooses to challenge that assumption, there will be some pretty tricky footwork required to make it all come out to a resolution.

Here are the possible triangles. Put one to work.

Note: These are all point-in-time snapshots. Could be the situation at the beginning or it could be after some story has gone by.

1. Alice must choose between Bob and Charlie.

Put Archie in the 'a' spot, Betty And Veronica in the other two.
Mega Man Legends: Volnutt is the A, with Roll Caskett at B and Tron Bonne at C
Kuno from Ranma 1/2 thinks he's in one of these with Akane and The Pigtailed Girl, but neither one wants anything to do with him.
This is what the main love triangle evolves into in To Love Ru, Rito as A, Lala and Haruna are B and C.
Maison Ikkoku: There are two of these that define the series.
- Godai (A) must choose between Kyoko (B) and Kozue (C)
- Kyoko (A) must choose between Godai (B) and Mitaka (C)
Pretty much the plot of Peach Girl - Momo must choose between Toji and Kairi. (Of course, there's also a ton of other characters involved, but this is still the main focus.)

2. Alice wants Bob, Bob wants Claire, and Claire wants Alice. This is the smallest interesting situation where All Love Is Unrequited.

See Twelfth Night: Orsino in the 'a' spot, Olivia at 'b', and Cesario/Viola on third.
Jean-Paul Sartre's play No Exit is a classic example.
The 1994 movie Threesome uses this setup with two men and a woman.
The manga Girl X Girl X Boy has one of these triangles most of the way through.
Natalia (Belarus), Ivan (Russia) and Toris (Lithuania) from Axis Powers Hetalia. With a twist: Belarus and Russia are siblings.

3. Bob and Charlie want Alice. Alice is neutral toward, or not initially thinking in romantic terms of Bob and Charlie, or thinking about them at all. Not a bad situation to be in, if you are Alice, though obviously a bit less so for Bob and Charlie. Some Alices will be tempted to see if there is any Type 7 (below) potential in the situation.

See Sabu: Osue is at 'a', in the sights of both Sabu and Eiji, two friends from childhood.
Ren (A) and his two best friends (a guy and a girl) in Kaze No Stigma, who are quite jealous of each other.
Anne (A), in Anne of Avonlea, with Chalie Sloane (B) and Gilbert Bylthe(C)- although it is hinted that she was in denial of a type 4 towards Gilbert all along, or even a type 7 with Roy and Gilbert in Anne of the Island
- Also Ayano and Katherine. Kazuma just exploits them both (not that way!) for fun, though.
Both versions of Mai-HiME contain type 3 triangles involving the main character(s):
- (anime) Reito (B) and Yuuichi (C) are both attracted to Mai (A).
- (manga) Yuuichi (A) is sought after by Mai (B) and Natsuki (C), since he is the "Key" to both of their HiME powers.
Naruto has Ino and Sakura pine after Sasuke's affections, but he is not in love with either. Similarly, Naruto and Lee have feelings for Sakura, but she rejects them both in favor of Sasuke.
- Sakura and Hinata over Naruto. Naruto is unwilling to believe that Sakura has feelings for him, and his reaction to Hinata's confession is unknown.
Idolmaster Xenoglossia has both Haruka (B) and Chihaya (C) with a crush on the same guy - Imber (A). Imber is oblivious to this - or unable to react, anyway - because Imber is a robot. Not a Ridiculously Human one - he's a Humongous Mecha. So Yeah.
One possible interpretation of the Takeru-Hikari-Daisuke triangle in Digimon Adventure 02, with Hikari at A while Takeru and Daisuke are at B and C. See next configuration for the second possibility.
In Clannad, both Ryou and Kyou Fujibayashi are in love with Tomoya, but he picks Nagisa over either of them.
The Best Years has both Devon and Trent in love with Samantha in the first season. This triangle is repeated in the second season with Rich and Jake.
This is how Touhou fanon portrays Marisa's effect on pretty much every other character she meets, but especially so with Patchouli and Alice. Marisa steals the precious things.
Maison Ikkoku: The majority of the series focuses on the pursuit of Kyoko (A) by Godai (B) and Mitaka (C)
Peanuts starts here. Peppermint Patty and Marcie are both shown interested in Charlie Brown. Chuck/Charles isn't quite noticing of them ...
In Full Metal Alchemist, this happens with Ed and Al (B and C) over Winry (A). Over time, there are hints that Ed's love for Winry may actually be mutual, which would potentially make it a type 4 if Al is still interested. Note that this is anime only, because in the manga it becomes quite obvious that Ed and Winry truly love each other, and Al isn't interested at all.
Girl Genius has Agatha (A), Gil (B), and Tarvek (C). Bit of a cross with Type 1, as Agatha likes both of them, and oscillates between which one she wants, but has not committed either way. An added twist is that Gil and Tarvek are each aware of the other, and hate each other (for reasons unrelated to Agatha, and have yet to be made clear).
- As of late, Agatha and Gil have started to express their feelings for each other, making this somewhat type four-ish (With Tarvek as A and Agatha at B). Predictably, when Agatha kisses Gil, Tarvek is not amused. That was still Gil in that last panel, he thought Agatha might have kissed Tarvek as well.
From Season 3 of Angel, Fred is A, Wesley and Gunn are B and C.
The Magical Girl Lyrical Nanoha Striker S 4komas have one with Fate and Subaru over Nanoha, and with Caro and Lutecia over Erio.
Trudy and Ki of General Protection Fault are both attracted to Nick, who is struggling with his feelings for the two of them and his own attitudes toward relationships. After Nick and Ki get together, this turns into a Type 4.
I Carly seems to imply this, with Sam (B) and Freddie (C) both having a crush on Carly (A).
In Axis Powers Hetalia, Greece (B) and Turkey (C) both like Japan (A) who backs out of telling them which one he prefers. Word Of God even dictates their relationships as Greece —> Japan <— Turkey. However, considering that the ratio of Ship Tease is heavily skewed towards Japan and Greece, many fans see this as more of a Type 4 triangle with Turkey at A, Japan at B, and Greece at C.

4. Alice wants Bob, who is already in a relationship with Claire. Bob is unaware/neutral (leaving Alice as a Hopeless Suitor), or is aware of the interest and can't/won't reciprocate. As the most complicated set of relations which is compatible with both monogamy and heterosexuality, this is very common.

Saki longing for Kurumi who is devoted to Nakahito in Steel Angel Kurumi.
Severus Snape, Lily Evans, and James Potter ended up this way, as revealed in Harry Potter and the Deathly Hallows.
- Also, for a short time, Harry (A) pining over Ginny (B) who is with Dean (C).
Eowyn, Aragorn and Arwen in Lord Of The Rings.
Lennier (A), Delenn (B), and Sheridan (C) in Babylon 5.
Ron (A) wants Kim Possible (B), who is already in a relationship with Erik (C). Ron won't make Kim aware of his feelings with Erik still around because.. well he's a You Suck compared to 'perfect' Erik, and Kim is too happy with Erik to think about Ron.
Justin, Elliot, and Sarah in El Goonish Shive. Justin's gay, Elliot's not. Earlier in El Goonish Shive, Nanase was in Sarah's place, with Sarah being in Justin's, and Elliot thinking Sarah's attraction to him isn't serious so doesn't respond for fear of damaging their friendship until the issue is forced.
Arrested Development: Michael is A, Marta is B, GOB is C. Later became type 7 (and briefly type 5) when Marta returned Michael's feelings, but not long afterwards she dumped both of them when they got in a fight over her.
In Faux Pas, both Cindy and Dusk are in love (or lust) with Randy, who believes that Dusk is more predatory than loving.
The movies Unlawful Entry and Indecent Proposal.
Frasier, for much of its run, with Niles at A, Daphne at B, and a series of Cs.
Eponine, Marius and Cosette in Les Miserables.
Yuzuru Narazaki (A), Yukari Fujimaru (B), and Ryo Katsuragi (C) in Penguin Revolution, first professionally (Yukari is Ryo's manager, and Yuzuru stages a very determined campaign to convince her to become his manager instead) and then romantically, with the added twist that as far as Yuzuru knows, Yukari is a man.
Pushing Daisies, with Olive at A, Ned at B and Chuck at C.
Mega Man Battle Network has Dex at A, with Maylu at B and Lan at C. Their NetNavis (GutsMan.EXE, Roll.EXE and MegaMan.EXE) are in the same positions.
Mega Man Star Force manages to do this with four characters: Luna Platz (A) is a very big Mega Man (B) fangirl, but is somewhat indifferent to Mega's regular-ego, Geo Stelar (also B), who has a close friendship with Idol Singer Sonia Strumm (C).
Disney's Beauty And The Beast: Gaston is A, Belle is B and the Beast is C.
Final Fantasy IV: Kain (A) is fond of Rosa (B), but she and Cecil (C) are in love with each other.
Cyrano de Bergerac is a classic (and tragic) example: Cyrano (A) is in love with Roxane (B), who in turn loves and is loved by Christian (C). The ugly Cyrano wants Roxane to be happy above all else, so he agrees to protect Christian as they go to war, while lending his poetry and wit to Christian to ensure he'll win Roxane's heart. It gets a bit more complicated by the end, but this arrangement is the basic premise.
May or may not have been the case in Metal Gear Solid 4, with Snake at point A and Otacon and Naomi in B and C.
College Roomies From Hell!!!: April is A, Mike and Marsha are B and C. Hilarity and bloodshed ensue.
- After Dave gets together with Blue and Margaret's Skater Boy Syndrome sets in, another one of these develops, with Margaret at A, Dave at B, and Blue at C.
Strawberry Panic centers on two of these triangles. The first consists of Tamao, Nagisa, and Shizuma as A, B, and C respectively; the second is Yaya, Hikari, and Amane.
The second possible interpretation for the Takeru-Hikari-Daisuke triangle in Digimon Adventure 02 has Daisuke/Davis at A, Hikari/Kari at B and Takeru/T.K. at C.
Fantastic Children gives us Sess(/Seth) as A, Tina as B and Soran as C.
Any given Ranma One Half triangle, with Ranma and Akane as the B/C couple, with any particular individual fiancee at A.
In Fans! this triangle arises with Rumi as A, Rikk as B and Alisin as C. That is until the situation turns into a contented 8.
The first three seasons of The Office (US) play out like this with Jim and Pam. In Seasons 1 and 2, Pam and Roy are engaged to be married but Jim is desperately in love with Pam. The role is reversed in Season 3 when Jim gets over his hopeless romance and starts dating Karen, while Pam realizes Jim isn't so bad and Roy is actually pretty rotten boyfriend material.
Brand Upon the Brain gets bonus points for diagramming this onscreen. Guy (a) and Sis (c) fall in love with Chance (b), and also with Wendy, (b in another triangle that has the same a and c.) The individual they think is Chance is actually Wendy in drag, so both triangles resolve in Sis's favor. (Guy faints when he realizes precisely what's going on.)
In General Protection Fault, the triangle between Trudy(a) and Ki(c) over Nick(b) is initially a Betty And Veronica triangle, but eventually, Nick gets into a relationship with Ki and Trudy tries to separate the two.
- Similarly, during Fooker(b)'s time working for the UGA after his cover is blown, Maddie(a) becomes attracted to him, while he's still loyal to Sharon(c), insisting that he should move on.
Occurs a lot in Zero No Tsukaima, with Saito at point B and Louise at point C. Saito is generally aware, but doesn't do anything too serious.
Fushigi Yuugi's main love triangle is in this format: Hotohori(A), Miaka(B), Tamahome(C).
- So is the secondary love triangle: Yui (A), Tamahome(B), Miaka(C).
- If you go by the theory that Yui is a Psycho Lesbian then there is also, Yui(A), Miaka(B), and Tamahome(C).
In the later Outlander books, Lord John is A, while Jamie and Claire are B and C.
Kimagure Orange Road pulls this one off nicely, with a slight twist. It does it twice. Hikaru is most definitely the A point, with Kyosuke at B and Madoka at C. They keep things somewhat hidden for the most part, however, from just about everyone except Madoka's boss at the cafe, and very occasionally, someone who won't say anything about it. Why? Hikaru is Madoka's friend from childhood, and she doesn't want to hurt her. Which makes Hikaru think Kyosuke is hers, which then turns it into the very next example mixed with, in Hikaru's mind at least, this example. Yuusaku, the unrequited boy that's loved her for years, at point A, Hikaru at point B, and Kyosuke at point C. The kicker is that Kyosuke thinks of her as a sister, and only really goes along with some of her antics because he just doesn't want to hurt her. Somewhat convoluted? Only in theory. Watch and see how simple it really plays out to be.
- This applies more to the anime than the manga. In the manga, he showed romantic interest in both of them, and even came pretty close to settling for Hikaru. In the anime, he remains completely faithful to Madoka from beginning to end, he just doesn't want hurt Hikaru or deal with trouble that it would bring.
Presumably happens with Jiraiya (A) who is attracted to Tsunade (B), who was briefly in a relationship with Dan (C) in Naruto.
In season 2 of Gundam 00, Andrei Smirnov wants Louise Halev/by, who is in a long-distance relationship with Saji Crossroad. Their corresponding points are already in their names.
While everyone wants Shiki Tohno in Tsukihime, the most 'love trianglesque' relationship would be both Ciel and Arcueid in love with Shiki, and him reciprocating based on what route you're playing. Canon ending is Arcueid. Akiha and Ciel also form a triangle, and Ciel loses again... no wonder she's so irritated in Kagetsu Tohya.
Mai-Otome (anime): Tomoe (A) is madly in love with Shizuru (B). Unbeknownst to her, Shizuru is already committed to Natsuki (C). However, Tomoe believes that Arika is the (C), and spends almost the entire anime attempting to bump her off.
The most likely theories concerning Ninjette (A), Thugboy (B), and Empowered (C) is that they make up type 4 or type 6. The letch decorating Emp's coffee table apparently wants it to eventually end up as type 8, but no luck so far.
Shakespeare's A Midsummer Nights Dream, Demetrius is A, Hermia is B, Lysander is C.
Cook/Effy/Freddie in Skins (A/B/C respectively) reaches this point at the end of series 3.
Mahou Sensei Negima has, as of chapter 252, an all-girls triangle with Setsuna and Konoka as the couple, and Tsukyomi in love with Setsuna. The latter apparently doesn't know about the former.
Breifly, (and This Troper means briefly) introduced in the Canadian series Life With Derek. Noel (A) garners feelings for Casey (B), who, at the time, was dating Max. Noel was shown as a sort of fuel for the reason Casey and Max broke up because Noel technically reintroduced her old interests to Casey that went away after she and Max got together, but a relationship never truly developed between them except until the episode Just Friends, where Casey wants to prove that a male and female can be just friends and uses Noel as an example, but Noel (still harboring a few feelings for Casey) assumes she wants to start a relationship. In the end, they decide to become Straight Will And Grace, which was VERY disappointing for This Troper.
- It seemed to simply get worse when Noel becomes Brother Chuck and Casey begins a relationship with Truman.
Warcraft III introduces the love relationships of Illidan, Tyrande and Malfurion. Illidan(A) Loves Tyrande(B)who has been in love with Malfurion (C) Who reciprocates affection towards her. One of the best Missions of Frozen Throne is where Illidan and Malfurion work together to save their mutual love.

5. Alice loves Bob, but Bob loves Claire. Claire doesn't have feelings for either. If Alice comes to realize it, it could end up as I Want My Beloved To Be Happy. Or attempted murder. Depends on the author. This can potentially involve more than three people, with Claire having feelings for David, David having feelings for Emily, and so forth.

Willow wants Xander who wants Buffy, particularly in the early part of season one. Once Buffy decides she wants Angel, it becomes quadrilateral. Ah, high school.
In Slam Dunk, Sakuragi is in love with Haruko, who is in love with Rukawa (who doesn't seems to be interested in anything but basketball).
Commonly seen in situations where A helps B to seduce C whilst either harbouring a crush all the time or developing one as the plot unfolds, ala School Days or American Pie 2.
Stingray: Atlanta wants Troy who wants Marina (in spite of which Atlanta likes Marina).
All's Well That Ends Well: Helena loves Bertram, who's attracted to Diana.
Some Kind of Wonderful has this sort of triangle with Watts as A, Keith as B, and Amanda as C.
Peanuts: Lucy (A) is (terribly) infatuated with Schroeder (B), who's only interested in playing his piano (C).
In Naruto Hinata has feelings for Naruto, Naruto and Lee have feelings for Sakura, and Sakura and Ino have feelings for Sasuke, who cares more about revenge than romance. In Kakashi Gaiden, Obito is in love with Rin, but never told her, and Rin is in love with Kakashi, who states he doesn't deserve her for abandoning her.
- Sakura confesses to Naruto, who isn't willing to accept it, and Lee's apparently still interested in her, getting quite shocked and upset at her confession.
Quite a few Miyuki Nakajima songs. Most well-known example is "Akujo," where the singer is A, the man she's singing to B, and Mariko C.
College Roomies From Hell!!! has one of these after Blue makes her entrance, with Blue at A, Dave at B, and Margaret at C. This later turns into a type 4, see above.
The Best Years had this love triangle in season one. Dawn had feelings for Trent, but he had feelings for Samantha instead.
Maison Ikkoku: A few more of the triangles from the series include:
- Kozue (A) wanting a deeper relationship with Godai (B) who pines after Kyoko (C)
- Yagami (A) wanting a relationship with her teacher Godai (B) who pines after Kyoko (C)
- Asuna (A) wanting a relationship with Mitaka (B) who pines after Kyoko (C)
School Rumble: Harima (A) pines after Tenma (B) who pines after Karasuma (C), who (at least initially) shows no interest in her or anyone.
- Of course this is only the main triangle from the start of the series. By the end, a rather expansive Love Dodecahedron has evolved.
The situation in the Legend of Zelda cartoons, edging on Type 4. Link (B) likes Zelda (C), who knows full well what a loser he is, and whenever she decides he's being cute enough to get a kiss, circumstances intervene. Meanwhile, Spryte (A) is in lust with Link, often bashing Zelda right before trying to come on to Link...who prefers his girls a little taller than three inches. (Incidentally, Spryte is one of the three girls in the series who he actually does get kissed by.)
For Most of My So Called Life, the Brian (A) - Angela (B) - Jordan (C) love triangle was of this type. Many people think it still is; the rest saw it mutate to #4. In "Life of Brian", it briefly became a rectangle with Delia (uh, A'?), but Brian quickly destroyed that with the Idiot Ball.

6. Alice wants Bob and Claire, who are already in a relationship. In this one, the "want" may not be sexual in nature, or some or all of the players could be gay/bisexual.

Tatewaki Kuno in Ranma 1/2 is the "a" in this scenario (although he doesn't know/won't admit it), with Ranma (as a girl) and Akane as "b" and "c". Arguably, "a" could be any of the others involved in this Love Dodecahedron.
Sailor Moon Fanon theorizes that Rei Hino (a), Mamoru Chiba (b), and Usagi Tsukino/Sailor Moon (c) are in this stage. In canon, their relationship was more of a type 4 triangle.
Played for (very uneasy or extraordinarily guilty) laughs in Rocky Horror Picture Show, in which Dr. Frank-N-Furter (a) seduces both Brad and Janet (b, c) with practically the same dialogue in back-to-back scenes. Yes, it's that kind of movie.
In the webcomic Boy Meets Boy, Tybalt (a) tries to seduce Harley (b) away from Mikhael (c), who used to be his boyfriend. It's implied that Tybalt still has residual feelings for Mikhael, so his fixation on Harley probably has to do with jealousy as much as with desire.
It's very easy (and entertaining) to read the Sid (a)/Michelle/Tony triangle in Skins this way.
Kyon and Mikuru (b and C) are mutually attracted to each other, while Haruhi (a) lusts after both. And Oharuhi-sama gets what she wants... Hilarity Ensues.
In the Ouran High School Host Club manga, Hikaru is a, Tamaki is b, and Haruhi is c. Tamaki and Haruhi are not, due to complicated circumstances in a relationship with one another yet in spite of a mutual attraction. Hikaru is attracted to Haruhi but also feels loyal to (and loves?) Tamaki.
Arguably the case in Honey and Clover with Shuji being the third wheel for Rika and her husband in the past. The rest of the series can't really be listed on this page.
In Rosario+Vampire, while Yukari is initially attracted to Moka, she eventually becomes attracted to Tsukune, too, after he and Moka save her life.
99% of Girl On Girl Is Hot scenarios (the girls being B and C, obviously), usually with A fervently wishing for a Type 8.
The anime ending of Kuroshitsuji implies this with Ciel (B), Elizabeth (C), and Sebastian (A), with Sebastian having already proven to have very strong feelings for Ciel and previously shown to be rather fond of Ciel's fiancee...and when Ciel is talking about Elizabeth as they boat down the River Styx, Sebastian's dialogue has implicit I Want My Beloved To Be Happy for Elizabeth while comforting Ciel in his last moments of technical life.

7. The classic "affair" set up. Alice is in a relationship with Bob, but she's also in a relationship with Charlie. Both Bob and Charlie don't know each other or suspect the other connection. Much of the drama/comedy comes from all the work needed to make sure that the space between B and C stays free from any sort of information flow. A lot of geography between the two helps, or maybe a good social divide.

Alternately, it can be more of a "polygamous" relationship, with B and C fully aware of the other's relationship with A, but either lacking any feelings toward one another, or actively disliking one another (but unable to do anything about it without potentially ceding A to her rival).

Casablanca falls into this category, with A=Ilse, B=Rick, C=Laszlo.
The Arthurian Love Triangle is generally portrayed as being either of this type, or of type #5.
An interesting take on this appears in Randall and Hopkirk (Deceased) wherein B (Marty) is dead. Normally this would leave A (Jeannie) and C (Jeff) to get on with things, but B has come back as a ghost only C can see, constantly haranguing him about it, leaving poor A oblivious to this.
Clint Eastwood, Lee Marvin and Jean Seberg in Paint Your Wagon. Not necessarily an affair, so much as both Clint and Sam are married to the female lead.
There's a version where everybody knows what's going on in If I Pay Thee Not In Gold (by Piers Anthony and Mercedes Lackey): Ware is some sort of magical entity (called a "demon" for want of a better term) who changes genders when he/she has sex; he/she also must have both partners be completely faithful to him/her, or he/she will cease to be. So he/she "marries" both the Protagonist (woman) and a man, and pretty much has to have sex with one right after the other in order to maintain his (prefered) masculine form. At one point, Ware must go somewhere without his mates, and they are seriously tempted to make out... but the thought of Ware vanishing brings them to their senses, and when he returns, he joyfully explains that he expected them to be tempted but the fact that he's still here means they were strong enough not to give in.
- While this situation might be strange enough for most of us from the get-go, it's even a little more complex in the book: the Heroine comes from a society where women rule and all men are servants or slaves, so while she warms to the idea of Ware being her equal in a relationship, it's a little harder for her when she has to adjust to the other man, who's from a society where men are not inferior, and isn't about to kowtow to her like every other man she's ever met.
"The Rangers Three" in "The Shadow of the Avatar" trilogy go somewhere here. Sharantyr just does not wants to abandon either and focus her attention on only one; Belkram and Itharr know this, but stay Vitriolic Best Buds they were.
A non-affair version in Mahou Sensei Negima: Both Nodoka and Yue are in love with Negi, who seems to have feelings for both of them.
- However, Nodoka's self-mind-reader reveals that her first choice of a "solution" is, in fact, an affair of sorts.
- That being said, Nodoka and Yue have strong feelings for each other as well (assumedly platonic), so this relationship may be more like a #8 than a #7.
Twilight has Jacob and Edward both after Bella. Eventually this is "fixed" when Jacob Imprinted on Bella's infant daughter.
While it was more a problem of attraction rather than infidelity, this was a problem faced by Peter Parker back when he was with Gwen Stacy and had some feelings (mostly shallow ones) for Mary Jane Watson. Gwen seemed to have won, though Mary Jane clocked up some points in overtime. We don't discuss One More Day.
- Reed and Sue are married with children, but Sue and Namor have had feelings for one another for years. They've only ever acted on them in alternate universes, but they've had a lot of alternate universes together.
A pretty common place for superheroes in general to be. Writers are often divided on whether or not characters should end up married or what have you, so they introduce multiple love interests to muddy the waters. See Superman (Clark and Lois or Lana), Nightwing (Dick and Starfire or Oracle), or Batman (Bruce and Catwoman or Talia. Or Zatanna, Wonder Woman, Sasha Bordeaux...)
The affair between Almasy and Katharine Clifton in The English Patient is either this (except that Almasy works with her husband, so isn't oblivious to her other relationship); or it's a Type 8, if you go with the Ho Yay.
Emily, Naomi and Katie more or less fit this in Skins. Emily is A, in that she and Naomi love each other (eventually - it takes a while for Naomi to reciprocate, meaning this starts as Type 10), she and Katie love each other, and Katie hates Naomi and wants her to fuck off and die. Oh, and Emily and Katie's love for each other stems from the fact that they're twins - you'd better believe that the show milks the Twincest vibe for all it's worth. (The drama is derived from Katie's fear that Naomi's interference will leave her on the wrong end of a Type 4, and her non-understanding of the fact that the triangle starts as Type 10 and not Type 4 - she's convinced that Naomi is the evil lesbian trying to steal her sister, when it's actually Emily who's crushing hard on Naomi...)
- The JJ/Cook/Freddie bromance ends up as this too - Cook and Freddie have been torn apart over Effy, and it's only the awesomeness of JJ that's left holding the Power Trio together.
There was an episode of Bones where Brennan decided that more than one relationship was only logical, as one person couldn't fulfill all of her needs. She wound up dating a good-looking guy who pleased her sexually but bored her intellectually, and a smart but unattractive guy she loved talking with. She insisted to Booth that they were both rational and mature, and would understand... if she ever told either of them. In the end, they found out and both of them dumped her.
In Tenchi Muyo, both Ayeka and Ryoko love Tenchi, and he loves them back. They also hate each other, and constantly scheme to be his sole posessor. Tenchi, for his part, successfully navigates his two relationships, keeping the two in a balance in which neither decides not being with him at all would be better than sharing him.
In The Phantom Of The Opera Christine must choose between Erik (the phantom) and Raoul. She loves both and both love her. Erik feels immediately threatened when Raoul first appears on the scene, although Raoul is not aware of Erik's presence until later. Erik attempts to kill Raoul and Raoul attempts to have Erik arrested. Christine, though conflicted, chooses to help Raoul unmask Erik. This has all been part of Erik's Xanatos Gambit however, but the The Power Of Love prevails on him to allow Christine and Raoul to be together and leave in peace.
The risque Touhou doujinshi "Doll Suite" takes the usual #3 love-triangle of Marisa/Alice/Patchouli and throws it into #7 territory, with Alice being (A). Marisa, in particular, seems unhappy about having to share Alice with Patchouli, but ends up agreeing to play nice.
This was apparently the situation in Umineko No Naku Koro Ni, with Rudolf being (A) and Kyrie and Asumu being (B) and (C). Of course, then came the Death Of The Hypotenuse, so this is all in backstory.
In Bleach, Orihime suggests something close to this effect. Though her feelings for Ichigo are ~~subtlely~~ obvious from the beginning of the manga, she eventually asks Rukia point-blank if she has feelings for Ichigo. Rukia denies this, and Orihime is actually disappointed because she feels that if they both loved Ichigo, they could gang up on him and the "girls would win".
Kashimashi Girl Meets Girl: Hazumu is A, Yasuna and Tomari are B and C.

8. Straight-up threesome. In polyamorous circles this is called a triad. Not necessarily sexual in nature.

Vyse, Aika, and Fina in Skies Of Arcadia. Whether "a" is Vyse or Fina is open to interpretation.
Marina, Ursula, and Vlad from Kim Stanley Robinson's Red Mars Trilogy seem to fall into this category, though we never see them closely enough to be entirely certain.
Eric, Beth, and Kory, the main characters of the first two books of the Bedlam's Bard series by Mercedes Lackey, are in one of these. Definitely sexual in this case; Kory is bi, Beth is attracted to both guys, and Eric spends the first book struggling with the idea that he is bi (although he doesn't struggle very hard). Results in a happy, magical (literally) threesome, at least for a while.
The movie version of Cabaret, although it's never really harmonious.
Seen in Paul Kidd's Talking Animal novel The Fangs Of Kaath when one of the three main protagonists, Raschid, marries BOTH of the others, Sandhri and Yariim, who have also been feeling a growing attraction towards each other.
Sora, Riku, and Kairi of Kingdom Hearts are heavily implied to have this kind of relationship (although it may not be sexual in nature).
In the (awesome) French film Les Chansons d'Amour, the main character and his girlfriend of several years start a three-way relationship with a co-worker of his.
In the Distant Finale of Shoujo Sect, this has become the case with Shinobu, Momoko, and Maya, after evolving from a type 4 at the end of the main arc (with Maya being attracted to Shinobu, who'd just started a relationship with Momoko but didn't mind Maya's feelings).
In an episode of Dark Angel there's a (throwaway) mention of a man who hired a detective agency on his wife only to learn that she has been cheating on him with his mistress. (What's left unresolved is whether he should consider it good or bad news.)
Hikaru, Lantis and Eagle in Magic Knight Rayearth end up as this - though Type 9 seems to apply, as well.
Grandia II, with Ryudo, Elena, and Millenia (at the end)
Serph, Sera, and Heat seem to end up in some variant of this at the end of Digital Devil Saga (assuming you made the right choices), though considering by the time it's completely resolved, A and B have literally become one hermaphroditic self as Seraph through the power of true love and enlightenment, it might not count.
Rentarou and twins Sara and Sojyu enjoy a happy relationship together in Futakoi Alternative. Fighting is not uncommon, but there’s no competition for affection or attention.

9. Bob and Charlie are attracted/loyal to each other but are also attracted/loyal to Alice.

Pick a Mary Sue fic (more specifically, any Relationship Sue fic). Mary Sue is at 'a', of course, and B and C are occupied by lesser mortals who have been enchanted away from their sexual identities, loyalties, duties, and all other responsibilities by the mesmerizing beauty of her violet eyes. Naturally, Mary Sue is too noble to allow them to depart the Righteous Path.
My Father The Hero, where a girl tells the boy she likes that her father, who has taken her on a holiday, is actually her lover. Wackiness ensues.
In Harry Potter, Ron and Hermione are a case of Opposites Attract. But one thing they do have in common is their shared loyalty/affection toward Harry.
In Final Fantasy VIII, Seifer's henchmen, Fujin and Raijin, are utterly loyal to him. As he grows more distant, they start to depend more and more on each other, eventually parting ways with their leader.
This type also applies to Sibling Triangles, such as the one in the manga Touch.
This variant occurs in Doctor Who. The Doctor at A, Jack at B, and Martha at C. The Doctor, wary of relationships to himself and Jack, tries to keep all three relationships platonic.
Delia(A), Eric(B) and Fitz(C) in Vanishing Acts by Jodi Picoult, only Delia and Eric are engaged, which makes it also have elements of Triang Relation #4. Fitz eventually gets Delia, though.
In "Peanuts", Peppermint Patty and Marcy are both fond of Charlie Brown but are often perceived to be more than just friends

10. Alice and Bob are in a relationship, but Bob is attracted to Claire. How sympathetically Bob is played depends on their gender. Similar to Type 4, but with a different point of view.

Simon's attraction to Jenny despite being in a relationship with Maggie in Teachers
Early Niles and Daphne again, this time with Maris at A, Niles at B and Daphne at C.
Angel: Lilah as A, Wesley as B and Fred as C.
The Best Years second most popular love triangle in season two where Noah is A, Robyn is B, and Kathryn is C
Maison Ikkoku: Kozue (A) is dating Godai (B) who is two wishy-washy to break up with her, while he pines over Kyoko (C)
Shaun Of The Dead: David (A) and Dianne (B) have a relationship but it turns out that David has an unrequited crush for Shaun's girlfriend Liz (C).

11. The classic affair set up with a twist. Alice is in a relationship with Bob and Charlie, but Bob becomes attracted/loyal to Charlie. Bob and Charlie may or may not know about the other's involvement with Alice. This situation is clearly the fault of Alice, who failed to control the information flow properly. Bad philanderer! No biscuit!

The interpretation of the Arthurian triangle that Marion Zimmer Bradley gives in The Mists of Avalon.
Incredibly, this is the resolution of the love triangle in Fans (at least where the original ending left things).
In Toradora, this is the case with Ryuuji (A), Minori (B) and Taiga (C). This is a very strange twist of Matchmaker Crush. Taiga is trying to set up Ryuuji (who starts to take care of her) with Minori (who is Taiga's best and initially only friend). Taiga develops an emotional dependence on Ryuuji, who develops feelings as well. It turns out that Minori already had a crush on Ryuuji, but also had strong feelings for Taiga. Taiga remains good friends, but doesn't quite reciprocate Minori's feelings. Since the Official Couple is actually the title of the show/novels, bummer for Minori. Since everyone in this triangle is too nice to betray anyone, this draws out for a while
Rose, Jack, and The Doctor. Rose would be a, Jack would be b, and The Doctor would be c. Rose and The Doctor are heavily implied to have feelings for one another in the first season of the new Doctor Who series. When Jack shows up, its obvious that there's something between him and Rose as well. However, while Jack initially simply seems to feel competitive towards The Doctor, the feelings seem to develop into... something else.
- However, it's clear that things won't go beyond flirting where Jack is concerned, and the Doctor tends to flirt back at him, making this an oddly chaste and playful 8.
Karla, Daken, and Lester of Marvel Comics Dark Avengers seem to be dancing around becoming this. Adding Daken's emotion controlling pheromones into the situation just complicates things further.

12. Alice and Charlie are in a relationship, often married, but Alice likes Bob and Bob likes/is loyal to Charlie. Depending on genders this can be a hilarious or very tragic set up.

The relationship between the main characters in Being John Malkovich.
The backstory to Slings And Arrows, with A being Ellen, B being Oliver, and C being Geoffrey.
In Arthurian legend, this is how the relationship between Guinevere (A), Lancelot (B), and Arthur (C) plays out, with Lance torn between his attraction to Gwen and his loyalty to Arthur.

13. Alice must choose between Bob and Charlie, but Bob is also attracted to Charlie. Could arise in a gay/bisexual situation, or could be non-sexual in nature. The non-sexual setup might be something like a boy (A) wants to please his dear old Mum (B) and wants to do naked things with his girl (C). Dear old Mum likes the girl, and monopolizes her attention with shopping trips and general girl-to-girl socializing stuffs that greatly reduce C's naked-fun time.

Penny And Aggie: Put Michelle at A, Stan at B, and Rich at C.
Candi: Bisexual Trevor is at A, having to choose between Laura at B and Matt at C. Laura is attracted to Matt, though she won't admit it.
Eric in That70s Show was in the second situation for an episode. He was dating Donna and loyal to his mother, Kitty. Kitty and Donna then start going out shopping and lunching, cutting down on Eric's happy naked fun time with Donna.
- Wouldn't that make it a category 12 then. since Donna and Kitty mutually like each other?
Fate Stay Night's sequel reveals a situation only implied before with Rider and Sakura in love with Shirou and Rider feeling supreme loyalty to Sakura. Her solution is a bit unique, though.