Addicts eventually love and need their drug of choice more than anything else in their life. This is an example of true insanity. So using logic to understand an alcoholic may not be the best approach.
Essentially every addict needs at least one enabler. Someone who makes it possible for him to continue his use of his drug. Early- and middle-stage alcoholics may have a whole group of enablers. They are bosses who look the other way when he's late or doesn't show, people who set ultimatums and allow "just one more chance," the government who sends him his "disability" check, friends who don't see a problem because he uses in the same manner as they do, wives who forgive and don't insist on a change of behavior, parents who fear that allowing the addict to "bottom out" may kill him. A very real fear and totally unpreventable without resorting to locking him up.
And, being allowed to feel true despair, the consequences of his actions, is the only motivator I know of to wake the dreamer from his deluded slumber. Pain is a gift to the addict. Nearly none of us stop a pleasant habit until the pain it causes is stronger than the pleasure it gives us.
It requires an extreme amount of emotional strength on the part of those who care for him to allow him to suffer his consequences. There is fear of loss involved. Most enabling is done out of love. But, paradoxically, it can make the person we love even more ill.
So my thought is figure out what you're doing which enables him to continue using and stop doing it. Not so easy when you get in the way of an addict and his drug. Steadfast statements of love and care and firm resolve not to make it easier for him to use or to deal with his consequences is the key. Much more easily said than done.
That's why millions of people who are attached to people with chemical health problems attend a group called Alanon. In that group, which was formed sometime in the thirties, people share their stories and support each other in what works to help their loved one to recover. They also learn how they have played a part in the chemical use and how to resist repeating behaviors which may be harmful to the addict, but which have seemed like the logical thing to do.
When a family member goes to treatment and the family fails to get involved they are missing an important rule of family life. None of us develop in a vacuum and a family has deeply ingrained habits which may promote health or deterioration. Everyone in the life of an addict getting involved in learning healthy methods to deal with addiction increases the probability of the addict getting well.
He's already gotten the message several times over. Has the rest of the family gotten on the same page?