Mein Bruder, der Vampir

Josh is about to turn 30; he's mentally retarded, and likes to play at being a vampire. His sister Nicole is 15, and dealing with her impending womanhood; middle brother Mike is the "normal" one - his latest conquest is Nadine. Nic is fixated on getting laid, and watches Mike and Nadine through the skylight with Josh. Josh also gets fixated on sex, though he has no clear idea what it's all about, and in particular on Nadine; to Mike's chagrin, she seems more interested in Josh than in him. (imdb)