"Amazing! An exact duplicate of your brother. Only with pigtails."A set of twins who look and act for all the world like they're identical, except for the miiiinor detail that one's male and the other's female. It's common—especially in drawn or animated media, where the creator has complete control over the appearance of the characters—to use brother-sister twins as being each other's Distaff Counterpart and Spear Counterpart. They often display identical twin tropes, such as Twin Telepathy or Synchronization - especially if they are Creepy Twins. It's a way to make sure that twins, even if they're not identical, are immediately identifiable as such if it's relevant to their characters, and there are no other visual cues to show that siblings are fraternal-twins instead of just regular brothers and sisters. If the two siblings drift apart at any point during the story, a Twin Desynch is likely, and often occurs at puberty when the secondary sexual characteristics start becoming more apparent. They are also portrayed as more prone to Twincest than other kinds of twins. In Real Life this would just fall under Strong Family Resemblance, and isn't all that common—any set of fraternal twins, opposite gender or otherwise, won't be any more likely to resemble each other than normal siblings, other than being exactly the same age. Unless, of course, one identical twin is transgender and the other isn't. Compare to the rare real-life phenomenon of semi-identical twins, where the twins have identical genes from their mother and different genes from their father, and thus can be the same sex or opposite sexes. This could lead to an Uncanny Family Resemblance if the sperms are similar enough. This trope is perhaps the most glaring example of Always Identical Twins. Compare Opposite-Sex Clone.
— Dr. Fidgel, 3-2-1 Penguins!
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Anime & Manga
- Sora and Nami Aoi from Aki Sora.
- Subverted in Axis Powers Hetalia. Switzerland and Liechtenstein look almost exactly alike save for their height and eyes, but they're actually adopted siblings who met each other right after World War I, when they were the nation-tan equivalent of older teenagers. It's safe to assume they are at least distantly related since they both represent Germanic nations, but it's not specified what they are to each other in this sense.
- Aya and Aki Mikage from Ayashi no Ceres, who are not only Half Identical Twins, they are also Reincarnations of ancestors of theirs, a husband and wife, adding a touch of Twincest.
- Hideyoshi and Yuuko in Baka and Test: Summon the Beasts. Hideyoshi is so feminine that without even crossdressing, he's mistaken for his own sister.
- Tatara and Sarasa in Basara: when Sarasa decides to impersonate her twin brother, she just cuts her hair and almost everybody believes she is Tatara — even Tatara's fiancée. However, it may be because people deeply want to believe it.
- In Bizenghast, Edaniel and his sister Elala look very similar, as to a small degree Edrear and Eniri, despite their different skin tones.(they were made from bits and pieces of leftover souls so they don't entirely resemble each other).
- Possibly Hansel and Gretel from Black Lagoon. They appear to be brother and sister, and are nicknamed "Vampire Twins", but it's never revealed whether they are different sexes or not. Confusing things further, they have switched roles on-screen at least once, by having "Gretel" remove "her" long-haired wig (revealing a haircut identical to "Hansel"'s, down to the color and style) and hand it to "him" to put on. As their highly stylized school uniforms are effectively unisex, the switch is flawless. It gets weirder in the end when (Hansel?) Gretel talks with both Hansel and Gretel's personality by (him?)herself. It's highly possible that they are same-gender full-identical twins who are just acting out separate gender roles. Though it's strongly implied that they are either transgender or were mutilated and forced into it, judging by the look on Rock's face when Gretel shows him. Squick in any way.
- This is lampshaded in a manga omake where it's stated the Animated Actors who "played" the twins are actually the same gender (female).
- In the omake where everyone's genders are switched, they look exactly the same.
- Lampshaded in Boku Ni Natta Watashi: "Is it even possible for fraternal twins to be completely identical?"
- The Hayasaka Twins from Busou Renkin. May also count under Twincest...
- Yukino and Kanade from Candy Boy. They're fraternal twin sisters but look similar besides their hair.
- In Castle Town Dandelion, there's Misaki and Haruka, which look similar enough despite obviously fraternal twins such that Haruka often wears Purely Aesthetic Glasses as Identical Twin ID Tag. Averted by Shuu and Kanade; viewers often forget they actually are twins.
- Suou and Shion from the second season of Darker Than Black. Explained by the fact that Suou is actually a copy that Shion made of himself, but because the copies he makes with his power always have one major difference from the original, Suou turned out female. Except it's not justified because even though the current Suou is a copy of Shion the original is still shown to be a half identical twin in the flashbacks she appears in. The fact that the current Suou looks like her younger self despite being a copy of her brother is evident of this.
- Mind Screw in any case.
- Subverted: In Detective Conan there's a pair of twins who look rather different, but have almost identical genes, to the point where the female twin's suicide is blamed on her brother/fiancé (she'd only just found out that they were related, and he didn't find out until after she was dead) because of skin that is stuck under a false nail, and he has to be bailed out by Conan-as-Kogoro. It's explained as the girl having been born with Turner Syndrome, where she was born with only one X chromosome. Presumably, this explains why they look so different.
- Terriermon and Lopmon in the Digimon franchise. In Digimon Tamers, they aren't related (Lopmon's a Heel Face Turned Deva who's introduced right before things heat up), but they still manage to get an accidental Twin Switch in the second movie. The part about them being of opposite gender technically only applies in the English dub, as Lopmon is male in the Japanese version, though the entire biological part is technically moot to begin with as Digimon are canonically of No Biological Sex.
- Android #17 and #18 from Dragon Ball Z, who would look identical if not for their different clothes and hair color.
- Kurt and Chloe Klik from Genesis of Aquarion, complete with Twin Telepathy.
- Jewelpet Twinkle: Alma and Yuuma are so alike that Alma easily passes for a boy with the right clothing, and Akari keeps referring to her as "the boy who looks like Yuuma" before they properly meet.
- The Endoh twins, Shizuna and Izuna, from Linebarrels of Iron.
- Mariya (a Creepy Crossdresser) and Shizu (a Sweet Polly Oliver) in Maria†Holic resemble each other exactly except for gender. Which is probably part of why they can crossdress so easily.
- Kanba and Masako in Mawaru-Penguindrum. It eventually gets lampshaded when Sanetoshi points out how physically similar they are as a part of a "Break Them by Talking" lecture that he delivers to Kanba as he's getting ready to use a Survival Strategy to revive Masako, who has recently gone through an Heroic Sacrifice for Kanba.
- Johan and Anna/Nina from Monster, who were dressed identically when children and were almost indistinguishable. It remains when they grow up, to the point that Johan disguises himself as a woman to hide, and when Nina arrives to the same town she's confused for her brother's female identity.
- Toki and Sagi of Naruto were very similar in appearance, to the extent that Toki was able to impersonate Sagi after his assassination.
- Yuki and Jun Kanzato from Persona -trinity soul- would fit this trope to the letter if Yuki's soul wasn't in Jun's body after her death. Jun also manages to keep a transplanted piece of his sister's brain in his head without any need for anti-rejection medications.
- Hiori and Lily from Phantom Thief Pokémon 7 look a lot alike, but they're opposite gender twins.
- Kurando and Mafuyu from Popcorn Avatar are this, to the point when the latter comes to visit Kurando's classmates mistake her for him crossdressing.
- Daisy and Violetta, children in Princess Knight and its sequel, Twin Knight. Not only do they have the same beauty spot on their left hands, but Violetta has to, like her nearly-homonym Viola from Twelfth Night, impersonate her brother. And it works.
- Kozue and Miki in Revolutionary Girl Utena, though their hair colors are different shades of blue. The Movie uses a cameo that simplifies the twinness by making their hair the same shade of blue.
- In the Italian dub of Sailor Moon Stars the gender bending Sailor Starlights were turned into this, making them separate characters to the Three Lights due to the complaints from Moral Guardians.
- In Samurai High School, Tsukiko and Kou don't look similar at all, but nobody in school ever notices when they swap places, they probably count.
- In Shugo Chara!, Nadeshiko's identical twin brother Nagihiko shows up when Amu visits her house. Immediately subverted in the exact same chapter, where it's revealed after she leaves that they're the exact same person.
- Thunder and Fire from Soul Eater were revealed to be this in the manga, when a powerup temporarily changed them into adults (Thunder is female, Fire is male).
- Atelier Lana's Star Trekker is about the adventures of Captain Aya Nakajima, with her First Officer and identical twin Brother Commander Homare Nakajima. From the explanation given in the manga:
These two each received half of their parents' genes and are identical twins thanks to biochemical composition.
- Sumeragi Subaru and his sister Hokuto from the anime and manga Tokyo Babylon and X1999. By the time Subaru is an adult he looks noticeably different from Hokuto with a longer face while she looks the same, since at this point she's appearing as a spirit and hasn't visibly aged, having died at 16 in the climax of Tokyo Babylon.
- Vassalord has two sets of these: Rayflo and Rayfell are actual Half-Identical Twins, while Charley and Cheryl are unrelated (as far as we know) but look uncannily similar.
- A chapter of Venus Versus Virus deals with a girl who asks Lucia and Sumire to help her brother deal with a Virus. Tsukuyo and her brother Youji look alike except for their hair lengths and attire. Tsukuyo has turned into a Virus and no one can see her anymore besides her brother, the girls, and Nahashi. Her brother instantly knew something was wrong with her and locked himself in his room. She is killed by Lucia at the end.
- Sora and Haruka from Yosuga no Sora. That they both have unisex names doesn't help.
- In Yu-Gi-Oh! 5D's, the twins Lua and Luka look so similar that at one point Lua successfully disguises himself as his sister by wearing her clothes and changing his hairstyle. He otherwise makes very little effort to pass himself off as Luka.
- In Welcome To Room 305 there was a rumor around his campus that Yoongsung was a crossdresser. They really were seeing his twin sister, Yoona. Yoona's hair color is lighter but otherwise they look very similar.
- From the Marvel Universe:
- Andrea & Andreas von Strucker (a.k.a. Fenris), and Jeanne-Marie (Aurora) & Jean-Paul (Northstar) Beaubier. Both have superpowers that are activated by touching each other, though the latter pair also have powers on their own.
- Brian and Betsy Braddock—aka Captain Britain and Psylocke—used to be half-identical (Betsy's Caucasian body was naturally blonde and resembled her brother a bit). They aren't any more due to Betsy dyeing her hair purple, then getting stuck in the body of an Asian woman (and dyeing her hair purple); hard to imagine anyone would think they are related at this point, let alone twins.
- Jean-Paul and Jeanne-Marie Baubier—aka Northstar and Aurora of Alpha Flight—started off this way too. Both had the same silvery-black hair and identical powers (super-speed, flight, and creating blinding light when they touch), and wore similar outfits with the only difference being half of a star on their opposing hips, symbolizing their synergy. However, when Aurora fell out with Northstar after he slut-shamed her (in addition to being tired of his abrasive and self-serving personality in general), she changed her costume to be different from his, and even had her boyfriend Sasquatch, a geneticist, alter her powers. The end result being that she isn't quite as fast but can generate light on her own.
- Trin and Kirby Richards-Banner, the twin grandchildren of Reed and Sue, in Marvel 100th Anniversary Special.
- The rare aversion to this trope in Marvel are Vanguard/Red Guardian and Darkstar of the Soviet Super Soldiers/Winterguard and X-Corporation. He's a redhead Husky Russkie and she's an icy blonde, nor do their powers resemble at all. He fires concussion blasts that he must focus through his hammer and sickle while she's a darkforce manipulator.
- In the original continuity of Legion of Super-Heroes, Lightning Lass easily posed as her dead brother for one story, but was revealed because she didn't have an Adam's Apple. Much later, it was shown that her planet is almost all twins, but the twins were generally depicted as identical.
- An interesting case was a story arc in the Buffy the Vampire Slayer comic (the "Season Zero" between "The Origin" and "Welcome to the Hellmouth", published in 2003) where she goes to Las Vegas. The villains are a pair of conjoined twins: a male vampire and a female mortal. They didn't particularly look alike, but the fact remains that conjoined twins are identical by definition and always the same sex, so a pair that are opposite sexes is a case of Artistic License – Biology.
- Somewhat squicky example from the 2000 AD strip Nikolai Dante: Alexandr and Alexandra Romanov are twins, lovers and specially enhanced killing machines that can create and throw nano-mines. Oh, and they can fuse themselves into one deadly grotesque, six limbed form.
- In Marvel Star Wars, Vila and Denin aren't exactly the same. You can see from the second link that Denin is taller and a little broader across the shoulders. Still, after Denin died Vila was able to impersonate him.
- Sidney and Toots the twins in the Bash Street Kids (a comic strip in The Beano).
- Zipi y Zape: The twins look exactly the same... except for their hair color.
- Torr and Tarra from Swordquest, who look completely identical except for their genders.
"A son and a daughter, as alike as two flowers from the same cutting!"
- Jason and Cheryl Blossom from Archie Comics are twin siblings with the same deep red hair. It only makes their incestuous feelings more disconcerting in Afterlife with Archie.
- Archie Comics' Sonic the Hedgehog gave Nack the Weasel a Canon Foreigner twin sister named Nic, who looks exactly like a female version of him, facially identical save for a ponytail and eyelashes. Strangely, on her entrance in one issue, the woman Nack is flirting with mistakes her for his wife.
- The Official Fanfiction University of Redwall has an excuse for this; in one of the original printings of the book Redwall, the character Killconey swapped between male and female pronouns thanks to a typographical error. (According to later printings he's meant to be male, in case you're wondering.) In the OFUR, this has resulted in there now being two of him, one male and one female. The female one is generally referred to as Konnie to avoid confusion. She's technically more of an Opposite-Sex Clone, but they think of each other as twins.
- In the Doctor Who fanfic Gemini, the last two surviving Time Lord test subjects of the military research facility are a genetically identical man "TL-13-Alpha" and woman "TL-13-Beta"
- Ash and Caiden from VOCALOID Forever, along with Rin and Len Kagamine listed below.
- Grodyn and Rhejya from The Servants Of Ungoliant.
- The Animaniacs fan series Zany To The Max has Zak Warner and his sister, Ko. Taken Up to Eleven by conjoining them.
- The roleplay group The Strex Family has Diego and Divina, who in addition to being half-identical are supremely creepy.
- The Beauvoi twins, Reynard and Hermione, from Be Careful are described as this, with Reynard being referred to by Lord Voldemort in one side-story as looking like a male version of Hermione, which is particularly notable given that their canon counterparts, Hermione Granger and Draco Malfoy are not related and bear no resemblance to one another at all.
- In a few Knights of the Old Republic fanfics, there would be both the male and female versions of the Player Character, which was both a nod to the Skywalker twins and a way to further obscure the Tomato Surprise by use of Collective Identity. This spread into Mass Effect where there'd be a John and Jane Shepherd co-leading the Normandy crew. This was probably the reasons why Mass Effect: Andromeda just shrugged and made a set of twins for the protagonists (though you only play as one of them).
Films — Animation
Films — Live-Action
- In Jack and Jill, Adam Sandler plays both of the title twins. This is even unintentionally lampshaded when one of Jack's co-workers asks if they are "identical or fraternal".
- Viola and Sebastian in She's the Man (which is loosely based on Shakespeare's Twelfth Night — see below) look so alike that Viola can pass for a young version of Sebastian.
- The protagonists of Les Messagers du Temps.
- In A Series of Unfortunate Events the Quagmire triplets are "absolutely identical," so how the Baudelaires tell whether they're talking to male Duncan or female Isadora is a mystery — although Isadora is illustrated with subtly longer hair. But at least the two brothers Duncan and Quigley never share a scene. Jacques and Kit are an aversion, as the book does not mention any similarity. At all. If anything, there's more similarity between Jacques and Olaf.
- The Cozy Twins in 13 Suspicious Incidents are another example.
- In Wolves of the Calla, the fifth book of Stephen King's The Dark Tower series, almost all births in the village where the story is set are Half-Identical Twins; this is an explicitly unnatural (and evil) effect, however.
- Ser Jaime and Queen Cersei Lannister of A Song of Ice and Fire. As kids, they looked so much alike that they would wear each others' clothes. The fact that their parents were cousins might have helped. They're also Twincestuous (with the implication that the narcissistic Cersei sees it as the closest she can get to Screw Yourself). When Jaime starts to grow a beard while spending time as a prisoner in the third book, he thinks to himself that Cersei will hate that it makes them look less alike, and it becomes a very important symbol of their growing distance.
- Another example of a guy who decided to grow a beard to defy this trope: Chronicles of the Kencyrath has heroine Jame and her Half-Identical Twin brother Torisen. Jame and Tori look really similar: Jame is quite androgynous, and Tori is a tad androgynous too—but they're ten years apart in age, thanks to some Year Outside, Hour Inside magic. And still, Jame is frequently mistaken for her brother. Once she's better known, he is mistaken for her too—but only once, because that's when he stops finding it amusing and decides to defy the trope by grow a beard.
- In Kathryn Lasky's Starbuck Twins Mystery series of books for children, fraternal twins Liberty and July Starbuck are described as indistinguishable from one another save for the fact that Liberty's hair is long, and her brother July's is short. They also display Twin Telepathy.
- As children, Thom and Alanna, of Tamora Pierce's Song of the Lioness series, were so much alike in face and body shape as to be mistaken for each other, if dressed alike, which they exploit so Alanna can train for a knight and Thom can be a mage. The only distinguishing feature of the twins at that time was the length of their hair. It stops applying once they're grown, as Alanna comments that Thom has grown taller than she when they meet as older teenagers.
- Continuing from the example of Star Wars above, Leia and Han's first two children, Jaina and Jacen Solo. Timothy Zahn, who wrote the novels in which they first appear, deliberately modeled them after the Luke/Leia duo. In this case, though, it makes a little bit more sense, since they are raised together.
- In Donna Tartt's The Secret History the twins start out similar, but in the end turn out to be two completely different people because one of them has a breakdown and the other turns into a Shrinking Violet.
- Heinlein's Time Enough for Love involves a couple of female genetic scientists creating a pair of Half-Identical Twins for Lazarus Long: two redheaded women named Lazuli and Lorelei, or Laz-Lor. Lazarus calls them his "identicals" even though they're not exactly, being girls. And then they engage in a threesome that is either Twincest, Brother–Sister Incest, or father-daughters incest, depending on how you interpret the relationship. Please keep in mind that Lazarus himself is a pretty blatant Author Avatar.
- Lazarus also bought a pair of slaves to free who had been produced by careful genetic engineering. Said engineering ensured that, while they were brother and sister, they had no genetic relationship (having been created from perfectly complimentary gametes, each bearing different halves of each parent's genes). They were sold as a novelty, with complete documentation included in the package. Since they know they're full siblings, they had to be taught why it wouldn't be a good idea for their children to produce children with each other.
- The legendary immortals known only as the Twins in Trudi Canavan's Age Of The Five trilogy appear to be this to begin with—they were originally not only identical, but conjoined. They separated themselves with magic to avoid detection, and some time afterwards, one of the twins changed from female to male using similar magic. It was really confusing how one could be female and the other male given their history, and the reference to 'the change' is really easy to miss...
- In Sheri S. Tepper's Sideshow, two of the main characters are conjoined twins of different genders. This is justified in that they were both born intersexed, with ambiguous genitalia. The doctors asked their parents for their opinion on what to do, and while the father was certain that the first one was male (the Virgin Mary had told him so), the mother thought it would be nice to have a little girl. Naturally, the two run into some problems at puberty, since they share a circulatory system, but they each identify as the gender they were assigned and raised as.
- Poppy Z. Brite's novel The Lazarus Heart features identical twins, one of whom is a transgender woman.
- In Maggody and the Moonbeams, Dahlia insists that her twins are "identical", because they look a lot alike to her and she's convinced it'll get them successful Hollywood careers. The contrary fact they're different sexes is ignored, as she doesn't actually know what "identical" means in this context.
- In Orlando Furioso, Ricardetto takes advantage of being always mistaken for Brademante to woo a princess who fell in love with his twin sister. He claims to have been turned into a man by a grateful water nymph.
- Jobeth and Tommy in Clive Barker's The Great and Secret Show.
- Averted in Lev AC Rosen’s All Men of Genius: Based on William Shakespeare’s Twelfth Night, Violet does disguise herself as her twin brother Ashton, but only to people that dont know them. People have no problem telling Violet/Ashton” and Ashton/“Ashton’s cousin Ashton” apart.
- Lawrence Sander's The Tomorrow File references a pair of opposite-sex "identical (and incestuous) twins" named Francis and Frances.
- The Murray twins, Poppet and Widget, in The Night Circus.
- In the Xanth series, there's Hiatus and Lacuna. Possibly justified, since Xanth pretty much runs on Artistic License – Biology.
- Veniss Underground has Nicholas and Nicola. Since they are Designer Babies, they were probably intentionally made that way.
- Taken Up to Eleven with Redwall's Marlfoxes, a family of seven siblings (may or may not be actual septuplets, given that they're foxes and could be one big litter) described as all looking almost identical.
- In A Taint in the Blood by S.M. Stirling, at first glance heroine Ellen mistakes her lover Adrian's twin sister Adrienne for him. Justified in that they're offspring of a highly inbred vampire-werewolf-sorcerer species.
- The Lockhart and Teague series has the Constant twins who look very similar, although Sebastian is slightly prettier.
- Power Rangers RPM has the peppy twin geniuses Gem and Gemma. They have several superficial differences if you look close enough, but you have to look very close- not because the differences are minor, because they aren't, but because the twins in question are just that single-minded.
- Justified in a Law & Order: Special Victims Unit episode, where what appear to be Half-Identical Twins turn out to have been born as identical twin males. One twin's genitals were badly injured by a botched circumcision, and a crackpot doctor convinced the parents he'd grow up happier if given a sex change to female (s/he wasn't).
- Tragically Truth in Television there was apparently a real rash of this kind of thing back in the 70s, when cutting edge thinkers had decided that gender was just a matter of socialization. Turns out it's a little more complicated than that. See Wikipedia: David Reimer. It happened more than once because the first doctor, John Money, who performed it wrote medical articles stating that the procedure went well without aftereffects, because he didn't like the results he got — they conflicted with his theory.
- The short lived FOX series Mental had the part about a botched circumcision resulting in a sex change. It was all fine, until the "girl" ended up lighting him/herself on fire for no apparent reason and kept seeing him/herself in the mirror without a face. The protagonist (a rebellious psychiatrist) realized what was going on. The "girl"'s true identity as a male was trying to push its way to the surface. "She" didn't even have proper female genitalia, just a prosthetic designed to look like one. The crackpot who convinced her father to do this planned to give "her" a vagina when "she" was 18. (Because every girl waits until she's 18 before having sex or having A Date with Rosie Palms, and wouldn't notice the difference because No Periods, Period is normal.) Naturally, when "her" boyfriend finds out the truth, he runs away in disgust. At the end, "she" gets a boyish haircut and decides to try to explore the male lifestyle, even though, without certain body parts, the experience would be far from complete.
- Butch Lesbian "Walter" from German series Hinter Gittern Der Frauenknast ("Behind Bars - the Women's Prison") has a twin brother who's apparently indistinguishable from her without his beard. They use this in one episode to change roles, allowing her to escape and him to get closer to several female prisoners.
- The Big Bang Theory averts this by giving Sheldon a fraternal twin sister, Missy, whose face does not resemble his. Sheldon explains the scientific errors behind this trope in his typical Sesquipedalian Loquaciousness. Howard replies, "Hallelujah!" (Missy is rather attractive.)
- Also averted on The Edison Twins: Annie is a redhead, while her twin Tom is blonde. (There was an even an episode in which they explained the concept of fraternal vs. identical twins.)
- Meanwhile, their younger brother Paul is a brunette!
- Little Lunch: Nobody knows which of Max and Elsa is which, even though they know one is male and one is female. The fact they both use the boys' toilets makes it more confusing, as does their tendency to speak simultaneously.
- Pictured above, Vocaloid's Rin and Len Kagamine are sometimes portrayed this way (they're colloquially referred to in the fanbase as "the twins"). Officially, they look similar (same eye color, same hair color), have the same surname, and are opposite genders, but whether they're twins, mirror images, or something else entirely has been intentionally left to anyone's interpretation by Word of God (although it should be noted that Len is canonically taller than Rin by a few centimeters, meaning that if they were twins they wouldn't actually be an example of this trope as far as their official portrayal goes). This ends up functional in that individual creators producing work with them are left free to make them twins, lovers, both, different versions of the same person, complete strangers, or whatever is necessary for the individual work. In fact, most works that do portray them as twins don't necessitate in-story that their faces look exactly alike (with one of the famous exceptions being their incarnations as Riliane and Allen in the Evillious Chronicles saga).
- Kit and Heloise, the twin children of The Phantom.
- Older Than Steam: Sebastian and Viola from William Shakespeare's Twelfth Night, are so much alike that people mistake Sebastian for Viola (who for reasons of plot has disguised herself as a man).
- Siegmund and Sieglinde from Die Walküre.
- Coricopat and Tantomile from Cats. Mungojerrie and Rumpleteazer also count if they're siblings and not mates.
- Vent and Aile in Mega Man ZX seem to be like this... That, or they're just two versions of the same person. It depends on where you look.
- Likewise, Raul and Fiona Gureden of Super Robot Wars Reversal were male and female versions of the same character. Upon immigrating into Super Robot Wars Original Generation, they turned into this trope. In The Moon Dwellers, this is applied to Akimi Akatsuki of Super Robot Wars GC; while the male retains the original name, the female is renamed into "Akemi".
- Palom and Porom from Final Fantasy IV may qualify for this: While the artwork, particularly the sprites, lack sufficient detail to be certain whether they were meant to be identical or simply share a number of similar traits and style of dress, there is a distinct theme of similarity coupled with reversal; not only the sexes, but elements of personality (Palom is boastful and rude, Porom reserved and polite [when not berating her brother]), their style of dress (both are pictured wearing red and green outfits, but one's is red where the other's is green, and vice versa), their use of magic (Palom uses the destructive Black Magic, Porom uses the healing/supportive White Magic), and hairstyle (the sprites show a right/left reversal between the two, otherwise being identical; the portraits show Porom's hair looking well-groomed and Palom's hair looking rather messy). However, by Final Fantasy IV: The After Years, puberty and years of different lifestyles have taken their toll, making them look very noticeably different from one another. Also Porom dyed her hair pink for no particular reason. That might make them seem a bit dissimilar.
- Alphinaud and Alisaie from Final Fantasy XIV are this in terms of looks, but their personalities are so different that Alphinaud serves as a major character throughout main plot, whilst Alisaie leaves soon after her introduction and is only important in the plot for the Binding Coil of Bahamut raid. Humorously, Alphinaud (the male twin) is frequently mistaken for Alisaie (the female twin), but not the otherway around.
- ...at least until the first expansion, where she's shown a few times spying on the Warriors of Darkness and eventually returns to the main plot (with slightly different dialogue depending on whether you did the Coil or not) and becomes instrumental to their defeat.
- In The Last Blade 2, a woman impersonates her dead twin brother, Kojiroh, a member of the Shinsengumi, in order to bring his killer to justice. She ends up living the rest of her life under the charade, taking on her brother's identity as a tribute to him.
- Alfred and Alexia in Resident Evil – Code: Veronica. In fact, the resemblance is so good that Alfred is able to convincingly pretend to be Alexia for several years after she was frozen in order to make people think she was still alive. Kind of explained in that they are really clones.
- Nox and Matin Catorce are identical brother and sister twins from Blind Justice ~Torn souls, Hurt Faiths~ by Zektbach in the beatmania series. Both twins also have special swords that are identical, although one represents Hope and the other Despair.
- Tate and Liza, twin Gym Leaders in Pokémon Ruby and Sapphire. They look so similar that it's a common mistake to think Tate is also a girl, thus making them fully identical.
- James and Francine Garrett, twin co-owners of the Atomic Wrangler in Fallout: New Vegas. Fran is... not attractive because of it.
- Ayra's children Larcei and Ulster, from Fire Emblem: Seisen no Keifu.
- Also Yumina and Yubello, from Fire Emblem: Monsho no Nazo
- And in Fire Emblem: The Sacred Stones, the twins Ephraim and Eirika. They also are the main characters.
- The male and female Morgans and the male and female Kanas being twins is a rather popular fanon among Fire Emblem Awakening and Fates fans.
- In a similar vein, the male and female Avatars of Awakening and Fates are sometimes made into twins in some works where they both exist at the same time, like Super Smash Bros.. To prevent confusion, one of them, usually Female Robin and Female Corrin, is given their Japanese name (Reflet and Kamui, respectively).
- Eagle Eye Mysteries: The title protagonists, Jake and Jennifer Eagle. Besides the obvious gender differences, he's a red-head and she's brown-haired.
- It's not normally obvious due to their normally different outfitsnote and hairstyles, but Rahal and his sister Rania Suikoden V are near-identical. When Rahal is required to disguise himself as a woman, the player is likely to not realize what happened at first, and instead wonder "How did Rania get here, and what happened to her glasses?"
- Subverted in BioShock Infinite. Robert and Rosalind Lutece seem to be this at first, though this is the least abnormal trait they display. They actually turn out to be different versions of the same person from parallel universes.
- In the Bleach video game The Third Phantom, we have the main protagonists Matsuri and Fujimaru Kudo, both have similar hair and eye colors and both are noted to have similarly enormous talent and spiritual pressure.
- Reynold and Wren from Costume Quest. The player chooses which one they want to play, the only real difference between the two being gender, and saves the one that they didn't choose.
- Isabelle and Digby from the Animal Crossing series look similar besides fur color and clothing. In Happy Home Designer, Digby insists on being called a twin brother, not a little brother.
- Prince Alaric and Princess Alana, in Cute Knight Kingdom. They're so identical that for a long time, they get away with pretending to be a single individual called Al. The observant player, however, will note that their eyes are different colors.
- In Odin Sphere, we have playable protagonist Velvet and her twin brother Ingway. While not exactly alike, both have similar features, share hair and eye colors, and have a tendency to wear rather Stripperiffic clothing.
- Mass Effect: Andromeda: The protagonist is established in the character creation screen as one of a set of opposite-sex fraternal twins, and the character model for your twin uses the same settings you have, only gender-inverted.
- Averted and lampshaded in Ever17. You is confused as to why Sara and the Kid don't have the same abilities or look similar despite being twins, at which point it's explained with some amusement that biology doesn't work like that.
- In the Murder Mystery Jisei, one of the main characters has an identical twin sister who you don't see until the end of the game. It turns out that she and her brother were private investigators, and she deliberately sent her brother in as a mole to check out the murder scene. She was the telepathic voice helping the protagonist to solve the crime all along.
- Averted to some extent with the demons Zepar and Furfur from Umineko: When They Cry, who are twins despite having differently coloured hair and different overall colour schemes—and then there's the fact that we don't know who's the boy and who's the girl. However, they do have the same eye colour and wear the exact same outfit.
- Pluto and Persephone in Anti Bunny in spite of being opposite genders, otherwise look nearly identical. Persephone tends to repeat anything Pluto says.
- Roger and Lily Pepitone in College Roomies from Hell!!!!!! (from which the trope takes its name).
- Walky and Sal in It's Walky!, Less so in Joyce and Walky. And not at all in Dumbing of Age, due to Art Evolution, with the fact that they do have differences (in particular, Sal claims Parental Favoritism for Walky because he "came out more white" while she has naturally kinky hair) is a point of contention between them. (Although it might be there on some level, as Walky has mentioned that he's been mistaken for Sal before.
- Elliot and Ellen from El Goonish Shive have decided to use this as a cover story for Ellen, who's Elliot's Opposite-Sex Clone.
- Samael and Mara from Picatrix are twins. In an added twist, Mara inherited none of the magical ability typical of their demonic race while Samael inherited double.
- Janus and Arthur from The Adventures of Wiglaf and Mordred, as illustrated here
- Kau and Shala from Drowtales, seen briefly as children where the only visual differences between them are different shades of blue for their eyes, Shala (the girl) having more prominent eyelashes and Kau (the boy) having spikier hair tied on the other side. This is averted after the timeskip where there are a number of obvious difference between them, the main one being that following usual drow sexual dimorphism Shala is noticeably taller than her brother, and after chapter 46 Kau gains tainted red eyes, but Shala only lives a few minutes after this happens anyway.
- Thoss and Thlassa of Juathuur.
- John and Jade from Homestuck. Even before The Reveal, they are very similar in appearance and behavior (much more so than Rose and Dave).
- Though this could be partly due to the fact that their biological parents looked pretty similar as well.
- Litter mates Bear and Bryony from Catena don't act alike, but except for their hair and Bear's chin they're pretty nearly identical. Their other sister Patches, on describing Bryony, even comments to Bear that "She looks like you, only, you know, pretty."
- Sam and April of Dragon City look identical aside from gender and April's glasses, but according to the Fourth-Wall Mail Slot they actually are identical, gender in dragons is influenced by incubation temperature (as in crocodiles) rather than genes. Every other set of twins in the comic are obviously fraternal, even having differently colored scales.
- Averted in Princess Chroma with April and Sonny, who look no more alike than any other brother and sister.
- In Questionable Content, people think that Claire and Clinton are this, but she's a couple years older than him. It also doesn't work because Claire's actually trans, so she was presumably raised as a male.
- Nila and Moki from Lost Nightmare.
- Ember and their sister Ariel in Blindsprings, with the variation of Ember being non-binary in gender identity, but biologically male. The only real visual difference is Ariel having longer hair.
- Averted in Operation Reboot with Shae and Zane, who are clearly fraternal twins.
- Red vs. Blue subverts this with North and South's faces—while both have very light blond/white hair, they look quite a bit different—but it's played fairly straight with their armor, which is subtly different colors of purple and green. When only one is on screen, it's hard to tell which it is unless they're standing next to someone (South is shorter than North) or you've gotten really good at picking out the different colors of purple (South is lighter and North is darker).
- Vex and Vax on Critical Role. Their official art depicts them with very similar features. The twins are also separated in Episode 20, and when another character asks Vax what his sister Vex looks like, he points at his own face.
- In The Adventure Zone, Lup is revealed to be Taako's twin sister. Justified in that Lup is trans, and her and her brother's general ambivalence to gendered fashions make the two's wardrobes very similar.
- Phil and Lil on Rugrats. One episode has the twins managing to distract a robber just by removing Lil's bow to make her look exactly like Phil. Although it could be argued that most babies look alike anyway, in the spinoff, where the kids are 10-13, Phil and Lil can still pass for each other with a simple change of clothes and a wig.
- Robbie and Rosie in the 1980s UK stop-motion kids' series Cockleshell Bay.
- The Wonder Twins from Superfriends, Zan and Jayna.
- In Justice League Unlimited, the Ultimen are based on the Superfriends team members who were created for the show instead of the comics. Their versions of the Wonder Twins, Downpour and Shifter, are so similar it's very difficult to tell them apart. Shifter doesn't have much in the way of the Most Common Superpower, so even examination of the chest area only works if they're standing side by side to compare. They even share a voice actor.
- Justified since they are not actually twins, but somewhere between clones and genetically engineered super beings.
- Scooter and Skeeter from Muppet Babies. Of course, appearance is where their similarity ends, as Scooter is a Hollywood Nerd and Skeeter is a total daredevil.
- Ben 10 episode "Camp Fear" features brother-sister twins who fit this trope to a T.
- Lem and Ada from the 1980's Strawberry Shortcake series. Supposedly only their dog, Sugar Woofer, could tell them apart, despite Ada wearing a bow and Lem wearing a hat at all times.
- Before the Retcon in King of the Hill, Peggy and her brother Hoyt were stated to look very much alike, however because of the retcon they look nothing like each other.
- The Interesting Twins from Beneath the Mountain in Codename: Kids Next Door.
- Desna and Eska, Avatar Korra's fraternal twin cousins, are described by The Legend of Korra writers as "androgynous, creepy twins." Played for Laughs when Bolin calls them both "pretty ladies" before Korra tells him Desna is a guy. (He then has to ask which one Desna is.)
- In 3-2-1 Penguins!, the only differences between Jason and Michelle are their outfits and Michelle's pigtails. As shown on this page's quote, Fidgel lampshades how alike they look.
- While extremely rare (only three to five known cases), there are cases in which otherwise identical twins can be of the opposite sex. More info here.
- One real-life occurrence that can produce boy-girl twins who are genetically identical (but who do not bear a strong visual resemblance), is when a zygote that is 46,XY (a normal healthy boy), undergoes incomplete mitosis in the womb. One of the resulting zygotes is 46,XY (still a healthy boy), and the other has a missing Y chromosome, and so is 45,X (a girl with Turner Syndrome). Genetically identical apart from the sex chromosomes, although Turner syndrome produces some fairly noticeable differences (physical and otherwise).
- Another case of different-sex identical twins involved twins both of whom had some 47,XXY and 46,XX and showed signs of Klinefelter's Syndrome. That being said, in this example its possible that a rigorous and expensive combination of surgery, drugs, and therapy could make the "unhealthy" male of a brother-sister twin pairing turn out "normal" if Klinefelter's Syndrome was detected early enough. However two major issues are: #1 such a scenario has not been medically documented, #2 it treads on the morality of recognizing transgender sexuality (as such actions would take the natural transgender twin and artificially turn them male).
- When two sperm fertilize one egg, which is rare, the resulting embryo almost never survives. However, there is a unique (in recorded history) case of "semi-identical twins": a pair that inherited exactly the same set of genes from their mother, but share only half from their father.
- There's also the less rare instance where fraternal twins of opposite sexes simply have such a strong family resemblance that they can pass for each other... at least til puberty, anyway. Even then, there are boys who are a bit Bishōnen, and girls who are a bit "masculine"-looking...
- Can happen when one identical twin is transgender and transitions later in life, or if a genetically male individual grows up female due to one of many medical situations where that could happen, whereas the other twin grows up male without the condition.
- As of 2011 there are now news stories about a pair of teenage identical twins where one is trans.
- Another example of this is transgender actress Laverne Cox of Orange Is the New Black, who has an identical twin brother, which was extremely convenient for flashback scenes showing Cox's character Sophia before her transition.
- Yet another notable example of this can be found in the case of Bunny and David Michael Bennett (Rabbit and The Spine) of Steam Powered Giraffe, in which Bunny is a trans woman, and both still have similar singing voices.
- Enforced in the tragic case of David Reimer, who was reassigned as a girl after a botched circumcision attempt.