I can't give advice, but I will tell you what I would do if it were MY brother:
Since there doesn't seem to be a lot of cohesiveness as a family about the subject, an intervention may not be the best choice. Plus, he would probably feel betrayed as far as the abuse issues are concerned.
I would probably write a heart-to-heart letter explaining my concern and letting him know that I am there when the time comes that he's comfortable talking about it. I WOULD include the fact that it is gut-wrenching to see him using alcohol to dull the pain and shame.
Sometimes in life we can only provide an open path for someone in the hope that they will take the chance and come to us for help.
The only time (I think) that you can or should step in would be if it's getting to the point that he's a threat to himself or others. In the meantime, provide a loving and safe atmosphere and hopefully he will trust enough to let go of some of that hidden shame, anger and sorrow.
Hope the info helps.
There are no unresolved issues - they just didn't resolve themselves the way we would have liked. "Grinder and Bandler - Neuro-Linguistic Programming"