First let me say a person can get a DUI and not have a drinking problem. However 2 DUI’s I would bet the “ranch” the person has a drinking problem.
Had he not drank he would now have Joint Custody, his drinking has created his problems. He needs to address his drinking problem; if he didn’t drink he would not have this problem.
I bet he has many, many problems in his life. He needs to get help with the drinking.
Perhaps with time he will get more visitation time with the children. In a few years if he can prove to the court he is sober it might be worth while to file a Motion to increase visitation.