Swinging is what it was at first for Hubby and me. It was his solution to a discrepancy between us sexually; I wanted to experiment and explore, and he'd already done all that in his younger days. So he said I could hook up with other men so I could try the things I wanted to try. (And of course he was also allowed to hook up with other women.) Our initial rules stated that no feelings beyond friendship were allowed with other partners, and I had to talk hubby into even allowing friendship.
It quickly became apparent that neither of us is cut out for swinging. Hubby prefers only having one sexual and/or romantic partner, and I need at least friendship to consider someone as a sexual partner. The whole thing with Guy really came out of the blue; I wasn't expecting it at all, and he and I lost a month and a half of the three months he was in my area because I was so afraid of how intense things were getting that I stopped seeing him. But once I was able to admit to myself--and to Hubby and Guy--how I felt, and both of them not only accepted it but were happy with it, the situation felt like the way it should have been all along.