That’s what I’ve been doing. I try to not show much reaction as possible since I know he feeds into it. I say what I need to say, and it’s done. For some reason, I find him always trying to extend the convo longer than it should and then it ends up with him trying to taunt me over something. I feel that he does this because he can no longer control me. So with the little power he thinks he has, he uses it.
About your cousin, she needs to listen to you. If he continues to make it hard on her, she should take it to court if she hasn’t already. It would make things a lotttt less stressful.