If you were in my office I could ask many questions regarding the situation but you are not.
The goal for you should be to improve the situation. Telling your father may or may not be the right thing to do. Would it lead to a divorce? What would your father do if he knew? Would a divorce be better for them? Would telling your father make the situation worse? These are all matters you should be trying to judge in this situation.
Also consider whether your father deserves honesty. What would your father do if he found out that you knew but you did not tell him?
If you believe that your father should be made aware of the affair, go to your mother with an ultimatum. Let her know that you are aware of the fact that she is involved with another man and having an affair. And that she has twenty-four hours to tell your father or you are going to tell him. She may say “okay I will tell him” and then you won’t have to. Or she may say “I just ended the affair” and then the two of you will need to decide if your father should be told or if – the affair is truly over- whether your father does not need to be made aware of the affair at this time.
I can’t be specific because I don’t know all of the specifics of your situation but I think it would be best to approach your mother with the information you have. Give her an ultimatum and hopefully the two of you will be able to find a solution that is best for the whole family.
Unfortunately, you are in the difficult position of having to essentially “referee” your parents’ relationship. It’s a challenge but keep your goal in mind; do what you can do to improve the situation and try to avoid doing anything that could make it worse.
According to Focus on the Family’s website, they “suggest that you draw a very definite line in the sand. Strong boundaries are healthy; “normalizing” brokenness is not. Let her know that you love her, but that this doesn’t necessarily mean you trust her. Remind her that she has deeply hurt everyone in the family by deciding to become involved with another man. Say something like, “I love you and care about you, but I don’t approve of this relationship.”
I wish you luck.
This article has been updated from the original version, which was originally published here on November 3, 2008.