This is a true story, which occurred many years ago with my ex-wife. We had been married about 7-8 years and had become somewhat "stale" in our sex life. My ex caught me once watching porn on a video I had rented from a video store with a "back room". It was about 2 hours long and had several different scenarios from female masturbation, lesbian sex, MF sex, FMF sex, and MFM sex. My ex really got into it and brought her vibrator out and we mutually masturbated many times over this video.
I must add that on several occasions in our early marriage, we had sexual experiences with her best friend Carol, who was going through a divorce. She had spent a few weekends at our house, and we ended up having an FMF experience several times. It was mostly playing and them sucking each other's tits. But that is another story.
So, after I had to return that video, I was happy that my ex got so into it. I rented more and more of the porn videos, and we repeated our fun. My ex started revealing her fantasies, which included other people. She said she wanted a three way with another male, since we had one with Carol. I asked who, and she said she didn't know, but we could invite someone.
We didn't really know how or what to say to a guy, but she fantasized about it often, cumming many times as she vocalized her desires while masturbating.
My cousin, JC, who came for weekend visits often, had come to visit one weekend. He and I were watching a porn video in the living room and my ex would come by and see us watching. He was wearing a jogging pair of pants, and his hardon was quite visible. I am sure she caught this as she kept walking back and forth.