Examples by author:
- F.M. Busby wrote a short story with a similar concept using Reincarnation instead of a Gender Bender. The hero dies and finds himself reborn in the past as the girl who will eventually become his beloved wife. He/she then gets to re-experience their life together from her perspective, eventually giving birth to a daughter who turns out to be (surprise, surprise) him/herself yet again, reborn once more into the past.
- Robert A. Heinlein:
- "—All You Zombies—": There is only one character in the story, who is both of his own parents, being a Hermaphrodite who lived first as a woman, then lost his female parts due to complications from giving birth and switched to living as a man, then went back in time and had sex with his female self in an attempt to save himself from that jerk who knocked him up and then disappeared on him, then realized that the jerk was himself. Meanwhile, the bartender/time-travelling secret agent who helped him go back in time went ahead nine months to kidnap him as a baby, then went back further in time to drop him off at an orphanage. Because the bartender is also him, only older, and he wants to ensure that the Stable Time Loop that is his own life remains stable.
- Time Enough for Love: Lazarus Long at first objects to screwing his own identical-twin female clones, but relents when they assure him it's no more than "Narcissus loving himself".
- John Varley's stories have often had this, including The Phantom of Kansas. A case of clone incest appears in the Gaea Trilogy novel Titan with the lab-cloned Polo sisters, who privately engage in behavior that's still illegal in Alabama.
Examples by work:
- A strange case in Sergey Lukyanenko's Autumn Visits when Anna has a "shower moment" with her not-quite-human duplicate Mary. It's not specified exactly what they do in the shower, but their mutual attraction is clear, although Anna's attraction is partly due to religious fervor (she believes Mary to be God). The not-quite-human duplicate of Author Avatar describes the event as "a real bad case of narcissism".
- The short story "Blood Sisters" by Joe Haldeman involves The Mafia cloning a young heiress in order to substitute the clone and get the inheritance. The clone doesn't want any part of the plan — she thinks of the original as her mother and doesn't want her murdered — and goes to a Private Detective to ask for help hiding from the Mob. When she finally meets the heiress, however, the mutual attraction is strong enough to overcome any qualms about being intimate with her mother. The detective comments, "I did wonder what you would call what they were doing. Was it a weird kind of incest? Transcendental masturbation?" At the end of the story, it's mentioned that original and clone openly being lovers "started a fad among the wealthy, being the first new sexual diversion since the invention of the vibrator".
- In "A Clone at Last", a short story by Bill Pronzini and Barry N. Malzberg, a man who has little luck with women commissions a female clone of himself. He waits until the clone is eighteen years old before he tries to seduce her to avoid being arrested for statutory rape.
- In Frederik Pohl's The Coming of the Quantum Cats, similar characters from a multitude of timelines mix and match during a cross-time war; when a slightly more advanced timeline decides to quarantine the others to avoid eddies in the space time continuum, a lot of editions get dumped on an uninhabited Earth, where multiple copies of a particularly unsavory mook decide to set up house together.
- The Darkover novel Two to Conquer has the main character meet up with an exact physical duplicate of himself. The expected interaction occurs.
- Not as squicky as it sounds in Downtiming the Nightside: by the time the hero/heroine hooks up with him/herself, they are essentially different people thanks to a Gender Bender, several time loops and the side effects of the book's time travel Applied Phlebotinum.
- Forgotten Realms: In the House of Serpents trilogy, Zelia (a female Snake Person psion) likes to use Mind Seed on handsome males. This power effectively puts a weaker clone of her mind into the victim, eventually replacing it. Then she has sex with them.
- In Goldfinger, when Goldfinger has captured Bond and expects him to talk (also to die), Bond steels himself, telling him "you can go ____ yourself." Goldfinger good-naturedly replies "Even I am not capable of that, Mister Bond!"
- Isaac Asimov wrote a parody of "Home on the Range" called "Home with my Clone" ("...with the Y chromosome turned to X").
- Imperial Radch: Each Radchaai spaceship AI controls a suite of formerly human "ancillary" Wetware Bodies that can be dozens or hundreds in number and who still have some of those pesky biological urges. Breq mentions that she used to have her ancillaries perform "maintenance" on each other when their hormones needed balancing out.
- Incarnations of Immortality: In With a Tangled Skein, Niobe kisses two alternate timeline versions of herself. Clearly justified, as Niobe is essentially described repeatedly as the most beautiful woman of her generation.
- The League of Peoples 'Verse: The main character in Commitment Hour spends the last few chapters of the book having "impure" thoughts about a female clone of himself. To make matters worse, their minds are linked to share memories between them, so she "hears" every one of the thoughts — and likes them. The end of the book strongly implies that the character ends up romantically involved with his own clone, while a third, hermaphrodite clone has a whole 'nother squick going on.
- Majyk by Accident: While the book doesn't get as far as sex, in Majyk by Design, a cat (talking, magical) named Scandal gets split up into a number of copies by villains (who can control the copies). By the end of the book, he reabsorbs them — except for the one representing his female side, who being just a kitten was useless to them and out of the fight. He's accelerating her maturation, for this trope's purpose, with her full encouragement. (They are the only two cats in this world...)
- The Man Who Folded Himself: The eponymous time traveler has sex with both male and female versions of himself, sometimes several at a time.
- MARZENA gives us Marian and Geni. Geni is actually a holographic AI clone of Marian created via mind-merging with a Blank Slate. To get access to the master computer, Marian and Geni need to combine their brain activities together by fully merging with each other, resulting in supernova ghostgasms.
- "Nine Lives", an early Ursula K. Le Guin story, has a set of ten clones, five male and five female, who join some place where there were already two normal people working. When the clones have sex with each other, one of the non-clones says, "Oh, let them have their damned incest!" and the other says, "Incest or masturbation?" (The clone-sex isn't a major plot point, just a part of showing how the clone-group can't relate properly to outsiders.)
- Parallelities by Alan Dean Foster not only has the main character bedding an alternate female version of himself while traveling through The Multiverse, he eventually finds an alternate Earth populated entirely by doubles of himself.
- Post-Self: while considered a taboo for many years, dating one's cocladists (copies of oneself that have gone on to live their own lives) is very much a thing one can do. Many within the Ode clade in particular, with their focus on self love, are quite fond of this. In Mitzvot, Jonas introduces True Name to Zacharias, who is actually a long-diverged fork of hers via May Then My Name, and uses their relationship as blackmail material.
- Chuck Tingle's Pounded in the Butt by My Own Butt is about, well, see title, although downplayed in that it's just the narrator's butt.
- The Psychology of Time Travel: Time travellers have a whole vocabulary built up around having sex with their past and future selves. One character, Ruby, muses on the narcissism involved in this unusual proclivity.
- Quarters: Vree is about to have sex with Gyhard in her brother's body, but then feels just how much her brother Bannon wants it (while he shares her body) and stops in disgust.
- In Redshirts, the main characters get the actor playing one of the stars of the television show they're characters on to help them when the character he plays seduces him (or not; they actually just talked).
- The Rook technically features this, as the character of Gestalt is one mind in four bodies, including a female twin. However, in this case it serves a 'practical' purpose; by conceiving a new body with their exact genetic material, Gestalt created the potential for it to become essentially immortal so long as it conceived new bodies.
- Used romantically with several pairings amongst the Literal Split Personalities in Scorpion Shards. They are soul mates, so to speak, but it gets a little weird when one of them realizes he can't fall in love with someone who isn't part of the group.
- In A Song of Ice and Fire, Cersei Lannister is having sex with her twin brother, and it's heavily implied to be because this is the closest she can get to having sex with herself. It's to the point that when Jaime Lannister returns to King's Landing looking different (having shaved his head and grown a beard), she is less attracted to him because they now look different.
- The protagonist in Robert L. Forward's Timemaster gets into a foursome with his wife, himself, and himself. Hey, it was her idea!
- Fifteen-year-old Henry finds an outlet for his pubescent sexual urges this way (and, it's implied, repeatedly) in The Time Traveler's Wife. For added fun, his father walks into the room and catches him (them?) in flagrante. Henry rationalizes having gay sex with himself as a parallel to masturbation, and the obvious course of action that "anyone" would take in his situation (thankfully, his eponymous wife never needs to hear about it).
