I'm in my 40's now but way back when I was in my early 20's me and DH split up for a few months over something stupid back when we had only been dating for about a year or so. During that time I bumped into on a night out a friend of his brothers and we started seeing each other quietly, it was purely sex and nothing more for me anyway, he may have had a bit of a crush for a while prior as it was him that did all the chasing. It was a bit messy, not my style at all and I ended it after a couple of months. Then a few months again after that I got back together with my ex who is now my DH of many years. I swore his friend to secrecy and have generally avoided him for many years as much as possible.
These days its getting much harder to avoid him, we all live in the same neighbourhood, and my husband, his brother, my SIL and his friend and his wife always want to socialise together, he's often at my house to see my husband or watch sports and there is a horrible tension between us which he seems to enjoy. He always makes little comments to me when we are out of ear shot and I just want to forget the whole thing. Its my policy just never to engage with him on this at all, obviously I will have to talk to him in the wider context of socialising but when he makes these comments I just blank him and I still try to avoid him if I can.
I am happily married and I think he is as well. Honestly it was the dumbest thing I ever done but then I thought I'd never see him again after a brief affair and out of all the guys they hung around with all those years ago he's the only one who is still around and in our lives. I don't really want to have to come clean and tell my DH everything, it will only upset him and its all so long ago so I just need to suck it up.
Let it be a lesson to everyone to mind who you have your fun with, they could still be hanging around like a bad smell years later.