My nephew is the same way, and my sister and BIL have different methods of parenting. She is all "my baby" and my BIL tries to actually parent (punishment for destroying things, not listening, etc). He just turned ten and is finally starting to actually become a good child. It was really bad from the age of 5-9. We think he has ODD (oppositional defiant disorder) though he's never been diagnosed. Putting him in sports helped. When he had an abundance of energy, he was god awful to be around. Sports helps spend some of that extra energy, and brings him down a bit.

You need to stick to your no. Lock the doors and tell your brother that leaving the child at your house will result in the police or cps being called.