Sometimes, stepparents become abnormally attracted to their step-children. This usually occurs when they become a stepparent later in their step-child's life. They don't view their step-child as their own and, as a result, lustful feelings can arise.
This usually occurs in men towards their step-daughters, but it can occur in other combinations as well. It's almost always non-consensual, though some rare pairings do result in a consensual relationship. Sometimes, this trope is inverted with someone coming onto their step-parent, instead of the other way around. This trope is usually unrelated to Wicked Stepmother. A wicked stepmother is usually physically or emotionally abusive, but very rarely do they delve into the realm of sexual abuse.
Despite also being biologically unrelated to their children, this almost never occurs in adopted parents, and when it does it's usually treated on par with biological Parental Incest. This is because most adopted parents adopt their kids at a relatively young age. Foster parents, however, sometimes get treated negatively due to either foster kids usually being older or stereotypes that people only foster for money, rather than because they genuinely care for kids.
- Hinako from Bitter Virgin Does Not Like Men because she was raped by her stepfather for several years. This resulted in two pregnancies before the age of 16. Her mother didn't believe her until the second pregnancy.
- Greg Roland from A Cruel God Reigns, whose sexual abuse of his stepson Jeremy is the plot of the first six volumes of the manga.
- In Yuureitou, Rika learns that her father Marube is likely not her biological father. He can't know for sure, but he knows that Rika's mom slept with several men besides him. Marube has been molesting his daughter for years (under the pretense of fatherly affection) and planned on raping her once she turns twenty.
- In Elfen Lied, it's revealed that Mayu was constantly molested by her stepfather, and when she told her mother this, she became jealous, and blamed Mayu for her husband not being physically interested in her. Eventually Mayu decides that she had enough and ran away, and was homeless until she was found (and eventually adopted) by Kouta and Yuka.
- In Spider-Man 2099, it's revealed that Tempest's step-father had set up hidden cameras all over the house and took countless pictures of her, much like a stalker. She wasn't even in her teens at the time.
- In the backstory for Cadence in For Better or for Worse, her stepfather is fairly open about his sexual attraction to her, making repeated attempts to grope or assault her. Her mother refuses to believe her or do anything about it, as shes heavily emotionally dependent on him.
- The Book of Henry: The plot of the film, as it were, centers around a plot to kill Glen Sickleman in order to save his stepdaughter from being abused, presumably sexually. When someone refers to him as her father at one point, she very pointedly corrects that person and calls him her stepfather.
- In Good Boys, the protagonists Max, Lucas, and Thor are trying to learn how to kiss so that Max can go to a kissing party he was invited to. In the course of searching the web for information, they stumble upon a "step-incest" porn video where a woman forces her stepson to have sex with him as punishment for looking at her in the shower.
Lucas: Is that what happens when you get a stepmom?
- In Lolita, the protagonist Humbert married Charlotte Haze precisely because he was attracted to her young daughter Dolores, a common tactic by pedophiles to get close to their victims.
- The Catcher in the Rye: There are some implications that Jane's alcoholic step-father is attracted to her.
- It's revealed late into The Color Purple that Celie's physically, emotionally, and sexually abusive father is actually her step-father. Her biological father died when she was too young to remember him.
- In Power, Omishto's stepfather Herman is described as making her strip naked so he can beat her with a belt, showing that he "had his eye" on her; her mother was aware, but never wanted to admit it to herself until the end of the story, and was in fact thought to be jealous of Herman's interest in her.
- The plot of Mythos Academy concerns Gwendolyn Frost who has the ability to read the history of anything - or anyone she touches. Upon discovering a hairbrush from one of her high school friends, she gained visions from said friend which showed that her friend's stepfather had been sexually abusing her and was even planning to move onto her friend's young sister later.
- Averted in a Judge Dee case where neither party was abusive (although because the step-parent was a concubine, both she and the stepson were the same age, which reduces the Squick factor). But according to the Tang code, Ting might as well have been having an affair with his own mother (the fact that he tried to murder his own father so they could be together and frame an innocent man for it didn't help), and the judge outright orders the pair to commit suicide to avoid dragging the family name even further into the mud (Ting's father had sacrificed many of his own men to further his career).
- This is implied in A Swiftly Tilting Planet when Meg is able to see visions of her mother-in-law's teen years. The mother-in-law's widowed mother married a man who physically abused his wife and stepson, and was not shy about making sexual advances toward his stepdaughter. It doesn't seem, from what we're shown, that it ever advanced as far as outright sexual abuse (probably so as not to scare younger readers), but the implication that he wanted to do it is clearly there.
- The climax of Eleanor & Park is Eleanor discovering that her stepfather has been writing increasingly creepy and sexual notes on her textbooks. Hes also been eyeing her for some time as well, and Eleanor fears that he might also go after her nine-year-old sister, Maisie. This results in her running away to her uncle and aunt with the help of Park.
- Becoming Elizabeth: The teenage Princess Elizabeth lives with her stepmother Catherine Parr and Parr's new husband Sir Thomas Seymour. Seymour presents himself as a charming rake and playfully enters Elizabeth's room in the mornings while only half dressed. These "romps" are true to the historic record and caused a scandal back then, as Seymour's intentions were not innocent.
- In season 5 of Dexter, Astor runs away with one of her new friends back to her old house to get drunk. Dexter is initially furious (Astor is only 12), but comes around when he discovers that the friend's stepdad is sexually abusive and Astor was trying to help her. He beats the guy up instead, since "disappearing" him would draw too much attention at that point.
- In The Passage, Shawna Babcock was sexually abused by her stepdad for years, and it's hinted that her mother knew about it. She finally murdered both her stepdad and her mom after they stole the cash that she had been saving so that she could run away from home.
- Played with in Legion (2017), where Syd once used her body-switching abilities to impersonate her mother, then tried to have sex with her mother's boyfriend. Unfortunately, she reverted back to her normal form partway through the act, and in order to get out of trouble, she claimed that the boyfriend had raped her.
- Veronica Mars: in the first season episode "The Girl Next Door", it turns out a neighbor of Veronica's was raped by her stepfather. When he and the neighbor's mother come to visit, the neighbor tries to shoot the stepfather, who gets the gun away and tries to shoot her, but Keith manages to save the day.
- In an episode of Law & Order: Criminal Intent, the detectives realize that a woman seduced her then 14-year-old stepson when her husband left them alone while he went off on a business trip. He is consequently the father of someone he believed to be his younger half-brother. Even creepier, her dialogue and behavior show that 20 years later, she is still lusting after him, acting incredibly jealous of and rude to his wife.
- Taboo: There's a degree of sexual tension between Lorna and her stepson James. She had no part in raising him however, given that he only met her after his father's death, and are about the same age anyway.
- Christian Troy hooks up with a young nurse and her cougar mother. While he's glad to fulfill a common male fantasy, he's rather disturbed when he learns that they sometimes involve the daughter's stepfather (Christian is himself the victim of child sexual abuse by his late stepfather). He throws them out of his apartment afterwards.
- Ava Moore is a significantly more messed-up example. She adopted a boy with her partner, then ran off and raised the child, Adrian, as her own son when the relationship ended. Ava is a sexual predator who prefers teenage boys, and Adrian was no exception. To complicate matters even further, she's also a transwoman.