It sounds like you have tried, with your parents and even with your brother. Unfortunately sometimes another person simply isn't capable, has their own demons and ways of thinking about things you can't change. You are just more open to healing than he is, sometimes that happens.

Also, I believe you when you share that often you went without so he could have things due to how your parents carried guilt about not having it together enough to raise him. A new car can't replace loving and caring or fix what has been hurt or broken between your father and your brother. Not even building him a house can fix or replace or fill the hole and anger your brother carried.

Somehow you have to find it within yourself to let go of what you had hoped for and focus on your own needs. I know that's not easy as I have been working on that myself. Often it's better to let go as it can bring up old hurts that interfere with things you need to focus more on in the now.

One thing I have learned by living life (I just turned 64) is that we come across many things we just don't know how to navigate. That can bring up some significant challenges someone faced when they were young and did not know how to navigate challenges then either.