Dollydo,
wow. You are right about the tentacles of addiction. I know that was tough to get through but it sure does sound like you did the right thing. I'm glad that you are not having to deal with all of that.
I work in the Surgical Trauma ICU and every week we have a situation just like that. The people that have alienated everyone do end up being a ward of the state and the medical team is then able to make the decisions for the person. What I have always seen is that this is handled professionally and with compassion. The decision making process is sound and keeps the family from having to feel guilty or responsible. Each of us should understand that this is definitely an option and it happens all of the time.
I'm glad that you shared this....it's a great example of having boundaries that are appropriate. I'm sorry for the exchange with his sister....she has a lot on her but I'm glad that you didn't take on an additional responsibility that is best handled by others.
Sending prayers to all involved.