What Are The Rights Of Co-renters?

If possible you can contact your city's Tenant's Rights Association. If he did not sign a lease, then he do not believe he has legal right to reside with you.  If he is causing problems while drunk, contact the police department...they can put him detox for 24 hours. Some states may do so for 30 days.

Alcoholism is a very difficult thing to deal with, because there are so many things that are affected by the alcohol. One person might be fully functional, and take care of all of their bills, personal things, and even the people around them.
Other alcoholics are selfish, they won't pay a bill, or take care of the people they say they love, and others let themselves go without caring about even themselves, to the point of personal hygene, tooth decay, and diseases brought about by the consumption of the alcohol.
There's the abuser, the paranoia filled drinker, and the one who halucinates or is terrified by something when they are drinking.
It would depend on the type of drinker you are dealing with here. Maybe, "dad", wants to pay the bill, and put himself on the lease, but would rather have some guidance in doing it.
Sometimes a gentle nudge is all you need to make someone realize the importance of what you are trying to get accomplished. Other people sometimes need a stronger word to get them motivated.
If I were you, I'd get him there, and make him see that this is important to you, and that you don't want to beat around the bush about it, and it's time to get it done.
If he doesn't seem ready to do this, then maybe he doesn't really want to take it seriously, and you shouldn't let him cause you to be evicted over his staying with you and causing problems. I hope this helps you out. Good luck.