[Quiet Man Cometh]

All I would say is set your own boundaries as to how you and your brother interact (such as when he is in your room or playing with your things) and lets your parents do what they will. If your parents have a problem, you will just have to stand your ground. At least if it's pertaining to your things, than there is a dividing line you can argue. At the very least, he might learn that you mean business, even if your parents don't.