Your post serves as a perfect example of why alcoholism is considered "the family disease". The alcoholics drinking/drugging affects everyone even remotely associated to them.
But to hear them tell it, "I'm only hurting myself". I'm guessing this is the most universally uttered phrase among alcoholic/addicts, and it's universally untrue.
You are right to realize that speaking to him, or your sister for that matter, is not likely to change anything. If your sister is in denial, perhaps you could lead by example by joining Alanon yourself, and learning all you can about alcoholism.
Alanon is for the "Family and Friends of Alcoholics", so you qualify for membership. I believe it would help you to learn better ways to cope with his sickness, and more importantly HER sickness. Because, believe me when I say, living with active alcoholism makes the non-drinker sick as well. I was bat-sh!t crazy when I finally got myself untangled from my axw.
Living with and dealing with an alcoholic is like living in Bizzoro Land, up is down, black is white, and everything I thought instinctively was the right thing to do, was wrong and visa versa. SR and Alanon can help you help her to sort out the best courses of action.
I hope you keep coming back and posting, there is a world of knowledge here.
Thanks and God bless us all,
Coyote