Urdu literature (particularly romantic digest novels and soap operas) does have storylines that look like brother-sister romance, but there is always a specific loophole to make it "Halal" (permissible) or tragic:
A critical distinction in Urdu narratives is between culturally accepted cousin-based "romantic" storylines and non-traditional sibling-focused fiction. Mera Piyaara Bhai Urdu Pages brother n sister sex urdu font stories
: The sister is often seen as the bearer of family honor, and the brother’s role is to guard this reputation. Romantic Storylines and "Cousin Culture" brother n sister sex urdu font stories