You can't make people grow up, that is a personal issue for him, but of course that doesn't mean you don't have choices. You have to look at his strengths and weakness, does he have a job? Is he acting in a responsible way, or is he just into going out with his friends and chugging beer as you say? If he is, then politely tell him, this is hurting the relationship. If it were you who were going with friends would he appreciate it?