Parental Incest

Mrs. Mulwray: She's my daughter.
Jake Gittes: [slapping her] I said, "I want the truth."
Mrs. Mulwray: She's my sister. [he slaps her again] She's my daughter. [slap] My sister, my daughter. [slap, slap]
Jake Gittes: I said, "I want the truth!" [throws her against the sofa]
Mrs. Mulwray: ...She's my sister and my daughter!...My father and I — understand?
— the infamous reveal from the movie Chinatown

Many a man before you, in his dreams, has shared his mother's bed.
— Jocasta, Oedipus Rex

About the one thing squickier than Brother Sister Incest and Twincest is incest between a parent and their child. Freud had a lot to say about the Oedipus and Electra complexes, and could find subtext in quite a lot of places. But in Big Screwed Up Families, Deadly Decadent Courts, particularly abusive households and elsewhere, one is likely to find examples of this trope.

When this trope shows up in media, it's usually used to highlight the specific psychological issues that a character has, particularly if it features in the Back Story of a Serial Killer or other psychopath, or to give an already nasty villain that extra bit of shudder factor. Incest between a father and daughter is often portrayed in media as being predatory on the part of the father, and in a lot of cases when it's revealed, it's a crossing of the Moral Event Horizon that serves to get the audience completely against the father in question. When the daughter is the aggressor in the relationship, it usually means the daughter is seriously twisted in some way or at least has serious issues. In cases of mother and son incest, the usual scenario is a case of a Beloved Smother or other Evil Matriarch who loves her son (often a Mommas Boy) in all the wrong ways, though there tends to be less focus on the predatory when compared to incestuous fathers and more focus on the issues of the son in question whether or not the mother or the son is the aggressor. Conversely, it's often played for comedy, with the son understandably freaked out due to the mother's advances.

This trope appears with step, foster or adoptive parents as well as biological ones, sometimes to Bowdlerise it somewhat, although the power dynamics are still much the same as in parent/child incest. The Hikaru Genji Plan is one way to Bowdlerise it still further — though not out of Squick range.

Also see Incest Is Relative, where the couple involved do not know they're related, also Brother Sister Incest and Kissing Cousins. When children who don't know any better innocently suggest this, it's Father I Want To Marry My Brother.

By the way, the only thing worse is probably grandparental incest.

EXAMPLE

Film: Three places for the 26, a French movie where Yves Montand plays himself and buxom sex bomb Mathilda May plays his illegitimate daughter Marion (a character created for the movie, not based on any real person). They meet and, not knowing that they are parent and child, feel attracted to each other and eventually have sex. The Reveal comes when Marion's mom finally tells her that Montand is her biological father. Marion isn't shocked or anything, she just makes an "oops!" face. Later, the two go tell Montand the truth. Montand, unlike Marion, is shocked, and looks at her daughter with a horrified face... but Marion just smiles and shrugs, which makes Montand relax and realize that Parental Incest is no such a big deal after all. They all become a happy family and the movie has a waffy end.

Literature: VC Andrews dealt with incest all over the board in her books, including between parents and children.

Real Life: Josef Fritzl, who imprisoned his daughter and fathered seven kids by her (in addition to the seven-counting-his-daughter that he sired by his wife).

Woody Allen and Soon-Yi Previn (he was her quasi-stepfather, being her adoptive mother's boyfriend, but still....)


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