My ex and I am divorced about 10 months. We have two boys 6 and 10. Mom has a serious boyfriend who is also still married. She has introduced him to the kids and the oldest knows he is still married but is getting a divorce. So far however to the best of my knowledge he has not filed yet. He and my ex got together soon immediately after we divorced. Anyhow, today the 10 year old tells me that yesterday he ran home form the neighbors house who was babysitting him and he walked into the house while the ex and her boyfriend were having sex. He didn't see anything but heard a bit and heard mom rushing to get dressed. He left and when the nest morning had a discussion with mom wherein she told him how they were both tested for disease and gave him sort of a safe sex talk. He wasn't showing her how upset he was. I picked him up in shortly after and he told me about it. I said well how are you feeling about that. He said he felt that Mom lied because she told him in the past they were only dating and now he feels that she hid from him the true nature of the relationship. He said he was kind of confused about why they were doing this when the boyfriend was married. He also expressed that Mom isn't paying enough attention to him and his brother when they are together. I am really having a hard time with this. I knew about the boyfriend and that he is married. Obviously a bad situation that the statistics say will not work out. But now accidently my son is having trust issues with his mom over this and he is samrt enough to sense there is something wrong with this. Mom and I spoke briefly about this and she is upset and also fears I will spin this against her with our son. I never would do this and have always expressed nothing but good thoughts about Mom to the kids. In this situation I told my son that mom and adults don;t have to tell kids everything and that mom can be trusted she doesn't lie etc. My question is am I taking this too lightly? Should I be upset with mom. I don't know what to think. I myself am not even dating yet so the boys get my undivided attention when I have them. Is there anything I should do? Am I reacting properly?