I think he should "step down" from being an enabler to his adult children. They are no longer his responsibility. Drug addicts are manipulators extraordinaire and if he quits coaching and devotes all his time to them and making up for lost childhood, blah, blah, blah, it will only serve to prevent them from dealing with their serious problems which are their's and no one else's . If they've got an issue, give them a tissue: