a history of anger....

So the burning question on my mind today is are we entitled or required to carry on the anger,pain, or hurt done to our parents many years ago?
Let me explain a little . See way back when i was little, shortly after my father was killed, my aunt and uncle decided to do something really stupid and mean to my mother. Well, she was able to prevent them from furthering there desires of destruction, which truth be told they wouldnt have gotten away wtih anyhow. So my brother and i were not allowed to associate with that side of the family for basically our entire childhood on into adulthood. In the past few yrs i have reassociated with them and developed some good relationships with my cousins. up until recentlythis was mildly tolerated by my mother.
However, I am now told that I have made my choice. Because I refuse to remain angry and support my mothers grudge against them. Granted what they tried to do was wrong and i ahve told them i felt that way. My cousins have nothing to do tiwth this battle. They were too young. Even still my mother refuses to have any assocaition even with them. And she is angry and hurtthat I would. So i ask is this right? Should I carry on the pain and hurt that she feels towards them or is it ok for me to make my amends and create new paths?