I am so sorry for what you are going through! I have struggled with trying to determine if I will cut my brother out of my life if he continues actively using. I say that I will, but then know that it will be difficult to follow through. It is hard when your family tries to hide the addiction from the outside world. My parents have told no one except for another couple that are friends. They haven't even told my aunt who has an addict son!
I understand your emotions related to a suicide attempt. When my brother was wandering in the road and was struck by a motorcycle, my parents swear he was trying to commit suicide, and I believe it was his intent as well. I was devastated. I found myself begging him not to hurt himself and wanting to check on him every minute of the day to be sure he didn't. I am finally realizing that while I would be devastated if he ever succeeded in committing suicide, I would not be able to hold myself responsible for his actions. That doesn't make it any easier though. It is impossible for us to watch them every second of every day.
I hope that your brother finds the strength to choose recovery and stick with it. I hope that we, as siblings, can find the peace we need as well. Hugs to you!