IIN my sister sits on my lap?

You should tell her its enough. This is disrespectful.

In my culture, in fact ALL black cultures in South Africa, its a disgusting thing to do as a woman. She should respect u as her brother and not wear short things around u and sit on u like that. Its even weird that she's ok with u getting a boner from her. So weird. What kind of a sister is he???

I know whenever my brother is around the house, i have to cover myself and dress appropriately. I cant be showing off my boobs and ass around my brother cause he is a man, u know what i'm trying to say.....Imagine your brother seeing all your assets, what is he supposed to think or do. Or how will he respect you as his sister...?