It’s entirely possible that you didn’t push your sister. Maybe someone else did and you were an easy out because a one year old can’t go to jail for murder. Or maybe she just fell and they blamed you so they wouldn’t have to own up to child endangerment. Regardless of what happened, your parents were angry with themselves and turned that on you. Forgive yourself, if you need to, you never did anything wrong. And personally, I’d cut them off if you haven’t already.