Reply To: Friends to Show us the way

That’s a great idea! Slowly bring him into your family life and allow her to ask questions, if one of those questions is if mom’s relationship with her boyfriend is sexual, be honest and tell her that their relationship is sexual and let her see that it is no threat to your marriage.
I would explain that, her mom needs her boyfriend just as she needs you and show her how happy you are that her mom has sex with him and reassure her that there are no problems with your marriage, just that her mom needs sex with him as a normal part of her relationship with him.