In the manga, it's discussed at length that they are Not Blood Siblings - but Keitaro treats Kanako as if they are.Throughout her attempted seduction of him she always refers to him as "big brother".even when half-naked and cuddling up to him. Love Hina Again features Keitaro's little step-sister Kanako, who wants to claim him for herself.And Dio fears her to death, with good reason - the gal's completely crazy, and not in a good way. Delphine from Last Exile has a similar fascination with her brother Dio.Koi Kaze plays this trope straight with two blood siblings who haven't seen each other since childhood.
hack//tasogare no udewa densetsu (epecially in the anime, where it's played mostly straight, moreso than the manga, where it's largely played for laughs) between protagonists Shugo and Rena that the series has become derisively known among critics as ".hack//Twincest".
Tetsuya Tsurugi and Jun Hono -the Official Couple- were two orphan kids Prof.