You already have the cat so no since in worrying about your brother at this point. I know you do not want Trible to go to the shelter so my suggestion is to try some calming medication for a while. I used to be so against drugs for cats but after Magoo I find myself suggesting this all the time. It just made the world of difference!
Like Magoo I think it would only be a short amount of time that he would need them. It really helps to calm them until they can get adjusted to everything. It sure would help Mina too. It isn't fair that she has to suffer while you are trying to do a wonderful thing for Trible. It usually helps take the edge off until they can learn to get along. I really suggest you try it so you can have peace and both cats can be in the same room at the same time.
{{{HUGS}}} to you for doing your best to help Trible, your brother, and Mina!!!