Oh yeah, marry his brother and you'll always be with him as a sister-in-law. Then slowly seduces him and one day he'd lose control and do the "unthinkable". After that it's just normal blackmail shenanigans, "Fuck me or I'll show this to your brother and he'll be devastated." bla bla blah, not knowing the brother is already jerking to it like the cuck he is.