x123, your situation sounds very difficult and I want to commend you even more for recognizing that the situation calls for you doing something about your anger toward your brother.

You describe him in a way that makes me think he might have Asperger's Syndrome or some form of high functioning autism. The fact that your mother considered him stubborn and you describe him as a robot sounds like some of the ways people describe people with Asperger's when there's a lack of understanding.

It's not possible for anyone here to make a diagnosis, but information can be provided. Here's an article from Psych Central that describes Asperger's.

Asperger?s Syndrome | Psych Central

When you see your therapist, you might ask if s/he can teach you about unconditional self and other acceptance. Even though you may not like the way your brother acts and may even deplore some of his behaviors, a therapist can teach you to value his humanity even as you recognize his problems.

It's possible your bro can't help it and he may not be able to change much. Often that's what makes us so angry at another person. We can see they're smart and yet they keep doing the same irritating thing over and over. It's as if they can't learn from their mistakes and it pisses us off. But if your bro does have something like Asperger's he may be struggling almost heroically to function as well as he does. Learning to accept him, despite whatever difficulties he may have, may set you free from your anger.

I wish you the best in your own therapy. Most of all, I wish you peace and acceptance within yourself.