I am so very, very sorry this is happening to you and your son. I wish I knew what to say to help but I can't think of anything. Hopefully others here will see your post and respond to it with really helpful ideas. There are books written for adults on how to deal with toxic people, including relatives. But it is whole other thing when there is verbal abuse of an 11 year old. What a heartbreaking situation. I hope someone here can help you and am so sorry I don't have any good ideas!