I'm so sorry this happened. I imagine you're feeling bad about it. I've had this happen to me, so I can empathize. But, please realize that you have no control over him, or anyone else, for that matter.
What I did to deal with this was detach: Still love my sibling, but respect their wishes for 'no contact'. I started letting my sibling follow their course, live their life, no matter how I felt about the 'mistakes' I thought they were making. I realzied that it's their life and they should live it the way they want. I let go of my desire to 'fix' their mistakes and help them.
It's really hard to watch someone we love go down what we consider to be (and may in reality be) the wrong path, but we have no choice in the matter. It's their life, not ours. All we can do is love them and pray for them. When they are ready, they will hopefully let us back into their life. This is what I mean by detachment.
hope you feel better.