What about PPO ? boleh ke your sis apply that ? Has there been any evidence that he berkasar physically with your sis ? If there is, PPO shud be the answer. Meantime, make sure the ladies and kids if out of the house, is to be accompanied with a male family...or at least, 2 adult ladies out together. Refrain from going out alone.
check AWARE website...possibly they do have hotline to offer immediate advice on such matter.