You can expose to your in laws whatever way you want... if you attack it as "He's sleeping with another man's WIFE and they have YOUNG CHILDREN" and you think that would get more support then go that route.
He may come around, but affairs are terribly seductive. My worry is you will start to get ILL ... LONG BEFORE he considers ending things with her.
Your confrontation is NOT an argument. Whatever he says is irrelevant.
If you want to ADD his counter claims INTO your script
1. Their marriage is hopeless?"
Is he a marriage counsellor? He has a crystal ball does he? Of course its not going well with him mounting this man's wife behind his back... what does he expect?
2. He can't abandon her now?
You are abandoning your SON instead. EVERY MINUTE you put into HER is a minuite you could put into repairing your marriage and your son's family - you are worried about HER? What about your marriage? What about abandoning your son or your wife? Ever thought about that? If she needs marriage help, send her to a PROFESSIONAL COUNSELLOR... SEX SESSIONS in a HOTEL ROOM with YOU is NOT HELPING HER MARRIAGE.. its DESTROYING YOURS
If you want to toss that in that's fine... Affair couples success rates are less than 1% long term.. he's a fool if he thinks he's saving her... he's just ruining those chidlren's famliy is what he's doing... THEY will grow up to HATE him for what he's doing.
You can try slow pitch with this man, but he's giving you classic addiction script and you will not be able to keep up that smile forever I promise you... it will get more painful the longer he cheats on you and attacks that other family.... you WILL lose respect for him and so will your son when he gets older...
I don't have the access you to do assess as well.. all I can do is read these posts and give you some of my thoughts from what I read here and elsewhere.
