Couple swapping with my dad and mother-in-law

Me and my wife have been married for 5 years now, together for a total of 7 years. Her mother has been single the entire time and it was because of her I met my wife, I had been hooking up with her and she then offered to set me up with her daughter who was same age as me, her daughter knew of my relationship with her mother but still accepted to start dating me. So we officially started dating, but that her mother was still into me and a bit jealous was obvious so could feel the tension on occasion but our overall relationship was still great, my wife back then because of the prior relationship was okay with me and her mother hooking up on occasion, but with the groundrule that only if she wasn’t around and I didn’t get her pregnant. Despite this things weren’t awkward.

Couple of years ago my dad divorced my mom and it didn’t take long before my mother in law took the opportunity to seduce him, they got together and half a year later they married. Some months after that my dad asked if we could talk in private and he revealed he knew of the relationship I used to have with his new wife, she had revealed it surprisingly early when they had gotten together. I said if he is worried we were still seeing each other then I can reassure him that it had stopped when they had gotten together, but he replied he was not worried about that, in fact they were interested in potentially expanding on that prior relationship. I asked what he meant and he said he doesn’t mean to be disrespectful and explained that they had been talking about couple swapping, involving other people and such and so they came up on the topic of the previous relationship between me and her, she still found me attractive and when she had asked if he also found her daughter/my wife attractive he admitted he of course did. So they agreed to allow each other to hook up with us, but without the first rule I had with my wife. It came as a surprise, but weirdly I did not feel against it, so when I came back home and told me wife about it and asked her opinion on it she was a bit shocked that had even come up and that our parents saw us this way, but she wasn’t immedietely dismissive of it and said she needed time to consider it.

The next morning while we were still in bed she brought it up again and asked what I wanted, I said I still found her mother attractive so it would be a lie to say I am not interested, and it would be hypocritical of me to deny her if she found my dad attractive, so if she is into this idea then I’d be up for it. She thought for a minute and then said we should try it then, I texted my dad that we are up for it and that evening we went over to their house. We had some snacks and after some talking we got to the topic and went to each our bedrooms, my dad and my wife went to his bedroom while me and my mother in law went to the guestroom. We started with some foreplay, touching, kissing and oral, but before we started going at it we stopped as we heard sounds from the other bedroom, we agreed to go peek a bit and went over to their door which was a bit open, he had already handcuffed her to the bed and was railing her, her loud moans and seeing her big tits jiggle was more of a turnon that I imagined it would be. We only watched for a moment then she started jerking me, pulled me a bit to the side and we started making out next to the door, then we went back to the guestroom, both of us more turned on than when we left. I had her lay on her side and lifted one of her legs above my shoulder and started railing her harder and faster with each thrust. She is a bit chubbier than my wife but their tits about same size, watching her body bounce just made me more in the mood. It felt amazing, I had really missed sleeping with her and she had missed being with me too, I ended up creampieing her and as we laid there catching our breath she turned to me and kissed me passionately, then said to keep it a secret and revealed she does wish I was the one she married, I didn’t say anything, I just smiled and kissed her back and we started on round two.

The day after things were surprisingly great, me and my wifes sex life has always been good, but this time she was extra energic and I think I was too, so we had a surprisingly good effect from it. As a result we started doing this coupleswapping on almost a weekly basis, even hooked up if we happen to be alone with each other. The idea of doing threesomes has come up but we never gone through with it, though the closest thing was that we started getting getting on with it while still in the livingroom but then move to our own bedrooms.