answer:You know what I’d do, call the police next time it happens and make sure you have your phone set to record. Record it. If he’s beating your sister up and feels so secure you and she won’t take it further, I’d make sure some burly cop showed up at the door and then had access to that recording. He involved you. He’s giving you proof there’s something going on there. If your sister can’t or won’t protect herself, but you’re being dragged into it, phone the cops. What an arsehole he must be.