I posted below, but it takes what it takes for a person to be miserable enough to decide to stop. If he finds himself homeless, that might be a catalyst for change. I posted my story below.

I was not able to stay away from Harold and my parents did not do that to me. There are some schools of though that suggest that, however, if it is making you sick, you have to take care of you. I would imagine, that even if he is at your house on the weekends, you are just glad to be with him. That is how I looked at it. You have told him no drinking at your house. If he is there, though, and is prone to seizures, in the 1940's, the men of AA used to keep some alcohol on hand to stop DT's, etc. I would not tell him that nor am I suggesting that is what you do. I do know, however, it is dangerous for an alcoholic (at least my type) to just stop cold turkey. It is good that you asked him not to drink at your house. Maybe he will get miserable and that is when people like me (and him) are most vulnerable and might seek help. I am so sorry and have probably posted too much. I think you are doing the best you can.