I've had similar problems with my brother, he most recently left a massive bruise on my shin where he kicked me as hard as he could, and bruises all over my arms where he'd been punching me. He's smacked my head against walls and pulled my hair, just ridiculous things really.
He's got bad anger issues and I think my parents are sorting out some counselling for him, maybe its something you could suggest to your parents and see how they respond to that?