I have set some boundaries. I have insisted that he never leave them alone with her, that they never act "in love" or in any way sexual around them, and that they never go out to dinner, etc., like a family.
You can ask for these boundaries but their is no guarantee that he will do them. And what are you going to do if they are broken?
Normally boudaries need to be something you can enforce.
Like if you continue to have a relationship with the OW I can not longer have a relationship with you.
