How could they possibly make a rule against that? There's no way the NCAA is going to get involved in trying to determine if his sister deserved a scholarship or not. And no way they're going to make a rule that says brothers/sisters can't both get scholarships at the same school. If that's what got them the recruit, then so what? Florida St. (or anybody else) could have offered her a scholarship too.
Edit to add: We didn't have a problem with recruiting Suh when his sister was on soccer scholarhship. And people were saying the same thing about UM giving a scholarship to Nkedemiche's brother, but he's playing and contributing for them, so there's no question he deserved a scholarship. Hell, we had his white brother on scholarship for a while ourselves.