AITA for refusing to save my estranged brother's life?

I never had a close relationship with my older brother, Mark. As kids, he was always cruel to me: he bullied me, mocked me in front of others, and once even blamed me for something he did, which led to me being severely punished by our parents. As we grew older, the distance between us only widened. We haven’t spoken in over a decade.

A few months ago, I received an unexpected call from my mom. Mark was gravely ill; his kidney was failing, and he needed a transplant. My mom begged me to get tested to see if I was a match. At first, I refused, reminding her of how much he had hurt me in the past. But the pressure from my family was relentless. I heard things like, “He’s your brother, your blood,” and “You can’t just let him die.”

Eventually, I agreed to get tested. It turned out I was a match, but even then, I wasn’t ready to take that step. Mark didn’t even try to reach out to me directly. Instead of apologizing or attempting to reconcile, he seemed to assume it was my duty to save him.

When I ultimately decided not to donate, my family turned against me. They called me selfish, heartless, and even my mom said she “expected more” from me. On the other hand, close friends have supported me, saying I shouldn’t feel obligated to sacrifice my health for someone who never treated me well.

Now I’m filled with doubt. Am I being cold and unfeeling for refusing, or is it fair to prioritize my well-being and the years of pain he caused me? Am I the bad person?