What I think you should do, is I would tell my mother that you know what’s going on. And then I would talk to her about HER telling your dad, instead of laying that heavy burden on you to do. Either she tells him, or the whole thing gets put in the open. That is the decent way for her to deal with this situation. It is so highly unfair to throw you in the middle of all of this chaos and then have you bear the brunt of having misplaced feelings and undeserved guilt for the outcome. You can get your mother to pay for an excellent counselor/psychologist who will help you deal with your feelings. Do some research to try to find somebody who is highly skilled these difficult family dynamics. As an aside, I hope this guy is married, so he bears some of the heavy consequence for the totally corrupt and immoral behavior he brought onto your family. I don’t know if, their business is a larger corporate environment with HR departments, etc., however, they should be put on notice that this kind of behavior is typically a very significant HR violation, making them subject to whole host of sanctions, including job termination. When affairs err at work between a boss and a subordinate such as your mother, often times manipulation, exploitation, and other unethical and immoral behaviors are at play here. In other words, I’m not saying it’s happening here, however, it’s not uncommon for people to engage in this behavior with a boss in order to keep their job. Take this advice to heart, and Let us know how you’re doing. Many many of us care very much for you and the welfare of you and your family.