My wife had a very intimate relationship with a girl in college. How would I navigate this topic with my son?

I (45M) learned last weekend that my wife (45F) had a very intimate relationship with a girl in college. She had hidden this from me because she thinks this is a very shameful thing, even though as I learned it happened more than 20 years ago. I feel that the way she hid it from me is wrong, but I also feel like I have to be very understanding. This was very unexpected for me, but I feel like I had to be very understanding.<br><br>We have a 16-year-old son and we both had a very open, very honest relationship with him—something that I felt very honored by. I feel very close to him and I feel like we had a relationship that most parents could only dream of. And now I feel like I have to hide something from him and that makes me feel like a horrible, horrible person.<br><br>I feel that I have to navigate this topic very carefully. I don’t want to break the trust between me, my wife, and our son. What steps should we take to navigate this topic?<br><br>It’s worth noting that my son is not very, very close with his mom.