When to move on?

My question is how do you know when to leave a relationship in the past vs when there is more work to do on it to manage your mind around it?

Over the last 5 years, I have had a very tumultuous relationship with my brother and his wife. In the last few months, we have reconnected again and started communicating, however I find myself between wanting to work for a better relationship and wanting to just move on and leave it in the past. I feel like their actions in the past were not in my best interest and they were to intentionally hurt me. During that time, I took on their thinking and took majority of the responsibilities for our family issues which put me into a deep depression. I want to try to make the relationship better, but I’m also worried that having the relationship will harm me in the future. I want to be someone who tries to mend the family, but I am reluctant because I don’t think my brother and his wife will change.