F. Compo

Masahiko Yanagiba lost both parents and, following his mother's will, moved to his maternal uncle's family, the Wakanaes. Although Wakanaes' hospitality was heartwarming, he soon found out why his other relatives shun away from the Wakanaes: his "uncle" is a woman while his "aunt" is just the opposite. Turns out the couple took the appearance of the opposite gender, and now Masahiko has no idea whether his cute cousin, Shion Wakanae, is either a boy or a girl.
(Source: Anime News Network)