Brother Sister Incest: Fairy Tales
- Sometimes used as a substitute for Parental Incest in fairy tales, such as Penta of the Chopped-Off Hands.
- In Princess Belle-Etoile, Belle-Etoile struggles with her feelings toward one of her brothers, Cheri, and his toward hers. Until she overhears a conversation between her parents, and finds they were actually all foundlings, and various things about them made even the parents think that he might not be her brother. In reality, he's her double first cousin.