He is already seeing the consequences of what he has done.
Keep in mind that your child is his child also. And, that he doesn't fully understand what is happening. He loves both his parents.
My ex doesn't have anyone that I know of so, it has been easier for me. But, after almost five years it will hurt if he does. And, especially if I see that he is attentive to her.
I think you x is asking your son to do this to justify what he has done.
Please take this to prayer ask God to give you strength.
Lately I have decided that sometimes keeping quiet is the best thing to do.
Like the other poster said..your x has gone on with his life now you must too.

After all this foofaraw with the "vows", my son has had enough. He is 17 and not a baby, and he can see his father for what he is: weak, insecure, needy, and incapable of being alone. Loves him dearly, but has lost 99% of the respect he had for his father. It makes me so sad...