No, he's not.
I also don't think that he was the one that killed her parents, but even if he was, that doesn't matter anyway.
Everyone knows Jerico was a raider, and would have killed heaps of people including little kids, but no-one bats an eye. Why should they be more suspicious just because they don't know Billy's past?
He's taking care of that child, that doesn't make him a 'pedo' or a bad person.
I think Billy being 'one of those', has the same chance of some people who think he is, are themselves.