If you have any contact with his family, I think you should make sure he knows through them of the confirmation, Then, if he doesn't go, it is entirely on him. He can't say, "She didn't let me go to my own D's confirmation" and play the victim.
I imagine most of his avoidance has to do with knowing everyone in church KNOWS. They dispise those situations. There is no getting around what they did, nor can they stand up and loudly proclaim how it was all our fault.
Take the higher road Goodfight. You'll have no regrets.
