We were married 15 years, 2 children, in a nudist club where their was a LOT of swinging going on, I had been trying for around 2 years to get the wife involved to no avail, (I was the only man she had been with, I took her cherry when we were 1
she knew I would do / give anything for her to join in the swinging scene, without going int too much detail, it finally happened when I was not there, "that's another story" Joe the guy she had it off with came around our place 2 days later with his wife Doris (who I had the hots for) with their children who played with our children at the nudist, the 4 of us talked about what had happened, naturally we all turned on, it was decided that Joe and the wife would go and have it off while Doris and I watched the kids, when they returned Doris and I went off to the bedroom to have it off, we just got started and their was a genital knock on the door, it was the wife "she wanted to watch", just to see what it was like, she was only there a few minuets and then left us to it.
I can tell you she did a lot of watching over the next 30 + years, so did I when we stated into M F M threesomes.