Caught in the act: Should I confront my cheating cousin’s wife?”

What should I do?  Should I confront my cousin’s wife, tell my cousin, or keep my mouth shut?

Today I was leaving the parking lot of BJ’s at 1PM.  My attention was drawn to a black SUV with an opened door.  At first I thought that someone accidentally left it open or that someone had broken into it because I didn’t see anyone on the outside putting in packages.  So I slowed down.  Then I was able to see that there were two people in the front seats of the SUV kissing and caressing. 40ish looking.  What the heck?  It surprised me that they weren’t teenagers and that they were making out in broad daylight.  A few things went through my mind.  One being that they must not be married.  There’s a reason why they were doing that in the parking lot.  The SUV looked familiar and then I recognized that it was my cousin’s wife with another man.  What the hell!  I was so upset that I almost hit a car.  I literally started talking to myself out loud.  Is she crazy?  I called my wife and she told me to stay out of it.  My cousin and I are close like brothers and I was the best man at his wedding about seven years ago.  My dilemma is, what is the right thing to do?  I don’t want to get in the middle of it, but I think my cousin should know, or maybe he already knows.  He works two jobs to support his family (including two sons), and they recently built a beautiful new home in the suburbs.  I don’t want to get involved because they could possibly break up.  It isn’t for me to judge, but I strongly feel like I am doing something wrong by not telling my cousin.