I never would have thought my SIL would be down for a threesome but oh man was I wrong. It came as a huge shock to me as she is very conservative and church going. She never talks about her sex life to anyone. Just recently she tied the knot and got married and it seems like that flipped a switch to her. I’ve been with her brother (my husband) for 10 years and have never seen her as wild as she has become in the last 2 months. With that being said, my husband and I hosted a party for their grandmother’s 75th birthday to which she came over to help set up table, chairs, decorations, etc… the morning of the party. While setting up she mentions that she forgot some table clothes that she had purchased at her house and that she needed to run back home and get them. She lives about 30 minutes away from our house so I tell her I’ll tag along so we can stop at the store on the way back to buy some last minute items. So we leave and this is where things got crazy. On the drive we’re chatting and she nonchalantly pulls out her phone and shows it to me and asks, “what is this?” I was in shock to find out that she was showing me my tinder profile that I use to look for couples and bulls for myself and husband. My profile clearly states what I’m looking for and she tells me that she kind of figured we were into some naughty stuff but could never tell and that this confirms her thoughts. She then tells me that she and her newly wed husband are swingers as well. They discovered the lifestyle while on their honeymoon and “there is no going back” she says. I’m was in shock. I never thought she had this side in her. She then starts asking details about myself and husband to which I tell her everything, the cheating, the taboo, the lifestyle…. She was just amazed by it all and so turned on. I could tell because as all this drive and conversation continues she is squirming in her seat and her breathing pattern changed tremendously. At this point we’re entering her subdivision and she bluntly asked if I would join her and her husband for a threesome. Without hesitation I said yes! I have always had thoughts of her and her husband is very attractive so it was an easy yes for me. As we get to her house and get inside, she wasted no time in telling her husband who is sitting on the couch playing his video game. She pulls me to their bedroom and starts kissing me and undressing me while her husband followed behind us. While still being in shock and all the adrenaline going it all seemed like such a blur. By the time I knew it, we had finished and were trying to rush to get back to the party to finish setting up. Our bond as sister in laws has definitely strengthened since then and we now talk daily. We’re trying to coordinate when we can get together again for our next adventure.