Same sort of thing happened to my wife and I. About 15 years ago when the internet was still fairly new, I got to private messaging a guy on a now-defunct hotwife forum. Neither one of us had actually shared our wives with others, or done any sort of lifestyle play, but it was a desire we both had.
Private messaging eventually turned into emails, and we discovered to our amazement that we only lived a few hours apart. After a year or so of communication and a growing friendship, our wives tentatively joined the conversation. Making a long, long story short and greatly simplifying, we four eventually met, eventually began playing together, became close friends, hotwifed back and forth, and generally had a wonderful time. The girls became as close as sisters, and my wife told me they shared things with each other they would not, in fact, tell their own sisters, all the while regularly enjoying the other husband's dick.
We four played together quite a lot. We started going on weekend vacations and motel rooming it together, sleeping with the other spouse and screwing half the nights away. At 2:00 in the morning I'd wake up with a hard-on, roll that wife over and start in. Usually all I had to do was look over at the other bed in the darkness and see my wife's heels pointed at the ceiling as she was getting laid as lustily as I was piping my friends wife.
Sometimes we'd trade spouses and go on hotwife dates, usually simultaneously, sometimes as a single pair. We did lots of vanilla social events too, which was all fun as well. Stuff like museums, theaters, movies, dining out. We even went to church quite a few times together.
All good things must come to an end, it seems, and so after about 10 years did our friendship with that couple. Sure was fun while it lasted though. It's a happening we haven't been able to repeat.