... This could have been a miniseries... all I really remember is young twins - A boy & girl - are possible orphaned?. The Girl goes to school & the boy works... one day the girl comes home & tells her brother that she heard about this thing that a boy & girl do together & she shows him... they have sex... anyway the girl comes home from school the next day & her brother is really angry with her & when she asks what's wrong, turns out he told some people @ work, what they'd done & all I remember him saying is "You Don't F*** Your Sister!"