If it was the other way around no brother I know of who is seriously into a woman would ever go for something like that.
Heck, I do not know too many women with the guts to even say such a thing to a man she is seeing.
It just never ceases to amaze me the types of things that some women will consider going for when their feelings are envolved.

I say this because I personally know of women who have gone along with a simular version of this senario.