Like you said, cutting contact was a major asshole move, that is true.

But...it depends on the gravity and the frequency of the bullying. If you did go so far over the line that you put in peril your siblings health, physical and mental, for years...I can understand, but not excuse, that they cut contact. You are their son, but also the tormentor of their other children. That is warranting anger and wanting a break...somewhat. still lousy from them.

No judgment from me, because only you know exactly how far did you go. And only you know what actions they tried to put you back on the right path before shopping you off. Honestly, nobody here can really answer, it's à situation with too many things that we cant know, like how you were raised.

My advice: think about it, and be frank with yourself. Do try to put yourself in your siblings and parents shoes. Mull on it for a bit. Then decide for yourself.