Two characters have a difficult relationship not because of their differences, but because of their similarities. This is most commonly seen between parents and children or romantic couples, but there's plenty of room for it in other relationships.
This can be a sign of self-loathing: the character hates himself, so he also hates people who remind him of himself. Or it can be a matter of certain traits needing to be complemented rather than mirrored in a relationship: someone who talks all the time and someone who would rather listen are obviously better off with each other than with partners like themselves.
See Foil for a list of examples of how differing personalities can be better together. Often overlaps with You Remind Me of X and You Are What You Hate. Compare Not So Different, Shadow Archetype, Hypocritical Humor, Turn Out Like His Father, Your Approval Fills Me with Shame, Doppelgänger Dating, and I Hate Past Me.
- Brave10: Rokuro and Nanakuma are a pair of Tsundere identical twins with Undying Loyalty to their respective masters, but that only fuels more conflict between them.
- Kaguya-sama: Love Is War: One reason Iino and Ishigami don't get along is because both of them are forthright and critical. Without other people around to mediate them, they just get deadlocked in endless arguments. There's also the fact that neither tells the other how they keep each other from harm. Iino did her best to keep Ishigami from being expelled in middle school and shields him from the other public morals committee members, while Ishigami secretly (and sometimes openly) does his best to spare her from humiliation or keeps her away from suspicious people. However, since they both think true altruism doesn't need any recognition, neither of them knows and interprets each other's actions as being hostile.
- Maria-sama ga Miteru: Sei and Suguru are basically the same character in male and female version. They can barely tolerate each other.
- Neon Genesis Evangelion: It's mentioned at some point that Asuka and Shinji are something like this, which comes across as somewhat humorous considering she's the poster-child for Fiery Redhead and he's a neurotic Extreme Doormat. However, later on it's revealed that they actually have very similar backgrounds — both having the same internal struggles and abandonment issues — and the main difference in is how they handle their problems.
- The Quintessential Quintuplets: Zigzagged with Nino and Itsuki, who have the most similarities between any of the sisters, namely being practical, realistic Tsundere who are nostalgic about the past. While this means that usually they're the two that get along with each other the best, one of these similarities is that they're also the two most stubborn and prideful of the quintuplets and the last two who accepted Fuutaro as their tutor, resulting in the two of them arguing with each other the most as well. The entire Seven Goodbyes Arc is kicked off by a massive clash between the two, stems from Itsuki calling out Nino's unfair treatment and rash judgment towards Fuutaro and her treatment towards Miku. While they both dislike Fuutaro (granted, the man himself acts jerkass towards her from time to time), Itsuki is more than willing to give him a chance and later learns more about him, while Nino barely even gives him a second thought and immediately judges him as an interloper and does illegal lengths to keep him away from her sisters. The youngest quintuplet's comments through the arc imply that they've had similarly fierce arguments in the past.
- Art Spiegelman, the author/narrator of Maus, mentions this off-hand to his fiancée, as he once had a girlfriend who was also Jewish and Middle-Class, but Art then mentions that because they were so similar that it was weird to get erotic with the girl.
- In one Betty and Veronica story, the titular girls bumped into two cute guys in the mall, Jon and Benny, who were pretty much their Spear Counterparts. By the end of the story, Betty and Veronica decided that they wouldn't make a good match because they have too much in common.
- In the Thor (2014) series, Lady Sif suggests this is why she and Thor never worked as a couple.
Thor: You speak your mind with the same fury with which you cross swords. 'Tis why I've always loved you, my lady.
Sif: Aye, and 'tis why our love has always ended so badly. I fear we are too much alike, you and I.
- Taken to an extreme in Calvin and Hobbes when Calvin completely clashes with his duplicate.
Hobbes: He's a duplicate of you, all right.
Calvin: What do you mean? This guy is a total jerk!
- Avengers: Infinity War: Tony Stark and Stephen Strange share a strong mutual dislike of the other, primarily because they're both Insufferable Genius Deadpan Snarkers who are evenly matched in both capacities.
- Fight Club: This is why the main character doesn't like the Love Interest, Marla, at first.
- Marriage Story: One trait that Nicole and Charlie both identify as liking about the other is competitiveness. Guess what happens when two highly competitive individuals who are married to each other decide that they both want to "win" the divorce proceedings?
- In Road to Perdition, Michael Sullivan, Jr., feels like The Unfavorite and eventually asks his father straight out if he liked Michael's murdered brother better. His father says that he didn't, and that if he treated them differently, it was because Michael reminded him of himself, and he didn't want his own son to Turn Out Like His Father.
- Chronicles of the Kencyrath: One of the key reasons Jame makes Torisen so uneasy is that she reflects back at him all the parts of himself that is uncomfortable with and represses—his Shadow Archetype. And yet at the same time, he loves her, and loving those parts of her helps him come to terms with them in himself.
- Goblin Slayer: High Elf Archer gets into an argument with the titular character because of their differing degrees of compassion: she wants to go after the big-picture enemies that are threats to everyone, and he's only interested in eliminating his personal nemeses, who have caused a lot of trauma to individuals but are not nearly strong enough to threaten civilization. The story takes the view that both characters have valid perspectives and could stand to learn from each other.
High Elf Archer: (distressed) Hordes of demons are going to attack! Do you realize that the world is at stake here?!
Goblin Slayer: Yes. But before the demons destroy the world, the goblins will destroy the villages.
- In Harry Potter and the Order of the Phoenix, Harry and Cho's relationship is sunk by their emotional volatility. Cho is so sensitive that she cries frequently over Cedric's death a year ago; Harry can't understand why anyone would succumb to sadness when there's still fighting to be done.
- The Hunger Games:
- Katniss and Gale. In the line when Katniss resolutely picks her other suitor over Gale, she cites this reason:
That what I need to survive is not Gale's fire, kindled with rage and hatred. I have plenty of fire myself. What I need is the dandelion in the spring. The bright yellow that means rebirth instead of destruction. The promise that life can go on, no matter how bad our losses. That it can be good again. And only Peeta can give me that.
- This is the reason Katniss and Haymitch have such a combative relationship—Peeta observes that they're far too much alike.
- Katniss and Gale. In the line when Katniss resolutely picks her other suitor over Gale, she cites this reason:
- I Favor The Villainess: Rei strongly dislikes Prince Rod Bauer for being determined, assertive, and unrelenting in his pursuit of whatever or whomever he wants. She displays the exact same traits when chasing her love interest, Claire. Ironically, Rod eventually finds himself quite smitten with Rei, though she unquestioningly, unfailingly rejects his advances—part because she doesn't like him, part because she's firmly, 100% lesbian.
- Jo and Laurie from Little Women are one of the most famous examples, although when Jo turns down his proposal she also points out the things that are too different about them (she wouldn't like high society, and he wouldn't like her writing). Laurie ends up marrying Amy, who is quite different than Jo.
- Malory Towers: The reason why Gwendoline can't stand Maureen: being around her is like looking in a mirror in an uncomfortable way. Maureen has all of her flaws and Gwen sees her the way the other girls see her which is a horrifying expierience for her.
- Percy Jackson: Percy and Thalia. This flares up when they are in the same line of command most of the time, but when they have their own chains they get along quite well.
Annabeth: You guys are so much alike it's scary. I mean, either you would've been best friends or you would've strangled each other.
- Red Mars Trilogy: Maya and Frank are attracted to each other, but they're both such Manipulative Bastards that it turns into a miserable time for both of them.
- A key element of the novel The Stone Angel is that Hagar Shipley insists that her younger son John is just like her while his older brother Marvin is like their father. In reality, the opposite is true and Hagar is simply deceiving herself. The stodgy, proper Marvin is just like his mother which is probably why she dislikes him so much.
- A Tree Grows in Brooklyn: Of Katie's two children, her daughter Francie takes after her—striking Katie as ordinary—while her younger son Neeley takes after his father, who was a handsome and loving but unreliable alcoholic. Katie devotes herself to making sure Neeley grows up to be like the man she fell in love with, but without his flaws, leaving Francie to fend for herself. She tries to hide her Parental Favoritism, but Francie understands her mother's motives instinctively.
- Tortall Universe: Alanna's relationship with Liam doesn't work out because they're such similar people: stubborn and temperamental warriors with Chronic Hero Syndrome who aren't willing to adjust for each other, or for anything. George (the man she marries) is a much more laid-back, humorous type.
- The Unexplored Summon://Blood-Sign: It's lampshaded that the war between Kyousuke and the White Queen will not end until one of them kills the other or converts them to their way of thinking. They're so proud and so driven to excel that it can't end any other way—even though, when they're not fighting over philosophical differences, they quite like each other.
- Babylon 5: this was the reason for John Sheridan's divorce from his first wife, Elizabeth Lochley. They had a lot in common, including their commanding dominant personalities. They quickly realized that getting married was a mistake, and claimed the divorce saved their friendship.
- The Borgias: Rodrigo and Cesare's increasingly strained relationship is in no small part because they're so similar to each other—"all the fire and the fury, the drive, the pitiless ambition"—which makes Cesare bridle at his constantly being denied real power, and Rodrigo's guilt for what they do gets exacerbated when he sees his own traits in Cesare. At the end of Season 2, Rodrigo starts to explain to Cesare that Rodrigo favoured Cesare's idiot younger brother Juan because Juan didn't continuously remind Rodrigo of his own faults, but the conversation is interrupted by Rodrigo being poisoned. The conversation finally gets finished at the end of Season 3 (after spending most of the intervening time undermining each other in various ways,) when Rodrigo blurts out to the man trying to reconcile them, "I look into his eyes, I see myself! Do you expect me to love that!?"
- Frasier: The recurring gag with Frasier's Sit Com Arch Nemesis, Cam Winston, was that Cam was almost exactly like Frasier, just slightly more successful at it.
- Monica's boyfriend Pete in Season 3, like her, was a Competition Freak and Control Freak. She eventually broke up with him because she couldn't deal with his stubborness. In the next episode, her easy going best friend Chandler implies he has feelings for her, laying the groundwork for them falling in love a season later. Their subsequent relationship and marriage is a very happy one.
- To a much lesser degree, Kathy, Chandler's last girlfriend before Monica also qualifies. They initially bond over their favourite tv shows and books and share a similar sense of humour. However in hindsight they both struggle with communication in a relationship and have Commitment Issues, which leads to their break up. The stable and level-headed Monica however, helps him overcome these problems rather than making them worse.
- Non-romantic example: When Rachel starts dating Ross's doppelganger, Ross is the only person (apart from Rachel) who doesn't notice the similarities. And he hates Russ.
Ross: And it takes him, what? ... like ... I dunno ... uh, hello? ... a week just to get out a sentence?
Chandler: Annoying, isn't it?
- House: Dr. House gets rid of one of his candidates because they think too much alike; the purpose of House's team is to challenge him and provide avenues of investigation he wouldn't have thought of alone.
- Red Dwarf:
- The episode "Me^2", in which Rimmer's self-loathing means that two copies of him end up unable to talk to each other, with one of them openly desiring the other's death.
- In "Parallel Universe", Lister and Rimmer meet their female versions. Dave Lister thinks Deb Lister is gross for a girl, but they avert the trope as they actually get on very well. However, Arnold Rimmer is completely disgusted by Arlene Rimmer.
- On Roseanne, the reason Roseanne and Darlene had such a tumultuous relationship during Darlene's teenage years is because Darlene is her mother's daughter to a T.
- Seinfeld: Jerry (being a narcissist) falls in love with a woman, played by Janeane Garofalo, because they have so much in common. He gradually realizes—being a self-loathing narcissist—what a mistake this is. He tells Elaine how it ended: they were sitting across from each other at Monk's when they both blurted out, "I hate you," and just like that they went their separate ways, still marveling over how they were always on the same page.
- Star Trek: Voyager: The Doctor gets a chance to meet his "father," the scientist who designed him. They clash immediately. Troi, who had been trying to counsel them, eventually gets tired of their crap and exclaims that she expected them to be similar but different, "like two sides of the same coin," but now she realizes that they're exactly alike—they're both jerks!
- Supernatural: While Sam's main issue with his father is that he and Dean were basically raised as child soldiers, after a Not So Different moment Dean notes that this was probably a factor as well.
Dean: Y'know, I finally get why you and Dad butted heads so much. You two are practically the same person.
- 30 Rock:
- Liz broke up with Carol for this reason, and later it was made explicit that she and Criss were a good fit because of their differences.
- There was an episode where Liz and Jenna had a fight and went looking for new best friends more like themselves, only to realize why they needed each other: Jenna is an Attention Whore who can't be around other people who will compete for the spotlight, and Liz is so negative that having another negative person to bounce off is just "exhausting"; she needs someone so vacuous and self-absorbed that they'll just let her vent because they're not even listening. (This helps answer the oft-asked and oft-lampshaded question of how these two were ever friends to begin with.)
- In Osaka Pro, Gamma was basically an expy of WCW, Toryumon System and Dragon Gate wrestler CIMA. CIMA wasn't too thrilled when Gamma jumped over and it would take years of fighting before the two finally became friends.
- Ring of Honor tag team The All Night Express were incredibly similar to Wrestling's Greatest Tag Team, even taking up similar entrance attire to the latter when they showed up in the promotion. Kenny King and Rhett Titus were quintessential jerk jocks who had spent their ROH careers belittling and bully any 'vulnerable' members of the roster but were none to pleased to be on the receiving end from Charlie Haas and Shelton Benjamin.
- Implied in Dragon Age: Inquisition. The one time Dorian mentions his betrothed, he strongly indicates that the two of them dislike each other for this reason.
- If (male) Shepard decides to break up with Miranda in Mass Effect 2, he uses this exact phrase.
Shepard: This won't work, Miranda. We're too much alike.
- In Fire Emblem: Three Houses, prince Dimitri and princess Edelgard are destined to fight each other no matter what route you take because they're both charismatic idealists willing to resort to violence to build the world they want. He's for the status quo, she is very much against it.
- In The Sims 3, most traits you can give a Sim strengthen the relationship when encountered in another Sim, but the "snob" trait conflicts with itself. Snobby Sims prefer someone with the "easily impressed" or "schmoozer" trait, who will agree that the snobby sim is superior.
- In El Goonish Shive, when Tedd plays Luke at Magickal Cards, neither of them seem to notice that it's practically a Mirror Match. They do, however, both think simultaneously "This guy has a really annoying play style."
- Sluggy Freelance: In "Oceans Unmoving", this is the core of the dynamic between Bun-bun and his Arch-Enemy Captain Blacksoul. Both of them are unbeatably badass Determinators who make everyone else do exactly as they want and don't have patience for much talk. In the same story's twist ending (so you have been warned), it's also revealed that Blacksoul is also Bun-bun, from a different time, disguised inside a powerful flying robot dressed in robes. He wants to follow his earlier self to find out how he got out of Timeless Space the first time, something he can't remember. He can't just reveal himself since he knows he'd attack anyone trying that since he knows the real him would know that and not try it. He's really annoyed at his other self by the end.
- Stand Still, Stay Silent: Lalli, who has low-key cat-oriented Delusions of Doghood, tends to have a difficult relationship with actual cats.
- Kaff Tagon in Schlock Mercenary has just enough traits in common with his father Karl that they don't get along for most of the comic. The biggest rupture came when Karl couldn't Shoot the Dog during a nanite attack, but expected Kaff to, despite neither being emotionally equipped for that.
- In Noob, Omega Zell is a misogynist and Gaea a woman who doesn't like being demeaned. Gaea, on the other hand, displays behaviors that Omega Zell tends to not approve of in general. Aside from this, the two don't get along simply from both being self-centered, ambitious and taking every opportunity they can to bring their goal closer. The situation is such that if one of them has a opportunity to make a big step toward their objective, they (often correctly) assume that the other has the same idea in mind.
- Alvin and Brittany in Alvin and the Chipmunks. When you have two Attention Whores with big egos headbutting, getting along isn't on the list of priorities as much as besting each other is.
- Eddy and Kevin in Ed, Edd n Eddy have many similarities. They are both the leader of their respective group of friends. They have both called Jimmy "Fluffy", which nobody else has. And in the episode "Fa la la la Ed", where the kids decided to celebrate Christmas in July, they both felt that it was stupid at first, while nobody else objected to it. But they are pretty much sworn enemies, because they also have two more similarities: they both want to be the most popular kid in the Cul-de-Sac (even though Eddy has no chance of beating Kevin in that department), and they can both be huge jerks.
- In Miraculous Ladybug, Gabriel feels so driven to protect the love of his life that he kills anyone who gets in the way of his plan to resurrect her. One of his intended victims is Marinette (superhero alias "Ladybug"), his son's Love Interest, which brings him into conflict with Gabriel.
- Gabriel is also this trope with Nathalie, who completely shares his goals. Unfortunately, she wants to achieve them by charging onto the frontlines and fighting, while he prefers a more strategic, passive approach that has less risks.
- She-Ra and the Princesses of Power has Shadow Weaver give this as the reason she was abusive towards Catra as a child. Both are highly ambitious individuals who resent those who are naturally gifted due to how hard they themselves had to work to get even a fraction of similar recognition. And since Shadow Weaver always had to struggle to get ahead in life, she figured it shouldn't be any different for Catra. Even if she wasn't fully sincere about this being at least one of the reasons she treated Catra so poorly, as she was intentionally playing on Catra's desperate need for affection as part of an escape plan at the time, the parallels are still there.
- Total Drama has Heather, the Queen Bee, and Courtney, the Type A. They are both contestants who are very strategic and highly determined for winning the competition and the cash money prize, but often do not get along each other very well, especially as teammates, primarily because of both of their frequently selfish and harsh behaviors towards others.
- This trope is the main reason why Drag Queens, despite being mostly gay men, are split on the idea of dating each other ("kai-kai"). Some are okay with it, while others see it as endless, exhausting Ham-to-Ham Combat and prefer to date quieter, more low-key men to balance out the crazy. This is precisely why RuPaul himself is married to a Wyoming cattle rancher.