When my mom found out my step-dad was cheating on her she was very upset, but I convince her not to tell him that she knew about it. I've told her that if she wanted, we could also have a good time and fuck when he's not around. At first she said no, but after the time passed and my step-dad was spending more time "at work", she realized it might be a good way to get her revenge. Now I make my mom moan good every time my step-dad is fucking his lover, and my mom doesn't even care about it any more.