I think Hubert has excellent advice!
We just recently got a new puppy. He's 12 months old and pretty big, but still acts like a puppy. Very playful, chews a lot, chases, etc. When he plays with us, he tries to bite us. Mostly typical puppy mouthing (love bites), but sometimes it really hurts. We've learned to just get up and walk away. Just after two weeks of this, he's realizing that when he makes contact with his teeth, he doesn't have anyone to play with. So the last few days he's really tapered off with the love bites. I promise it works!
I hate to equate your brother to a dog, but if you don't play his mind games, he will eventually stop. If he realizes that he can't ever get a reaction from you, then he'll quit. It will take lots of patience and time, but eventually he'll realize he looks like the idiot, not you. When other people witness your reaction, it might spur them to do the similar thing. With nobody in the family playing his head games, he'll straighten up.