(((Gizmo)))
We can't control how others turn out and separating a toxic element was obviously the best choice for you and your family.
I've had to make the same choice in the past when a cousin of mine was found guilty of second degree murder. I knew him growing up but as his behaviour began to sour, we had to go our separate ways.
It is surreal. Trying to wrap your head around a relative taking another's life - yes surreal. It's not on you and has nothing to do with you other than a past connection. Keep that separation. Protect yourself from his impact on your family, allow the compassion, this is your strength.