A couple months ago my sister inlaw came to hang out with husband and I, we had a few drinks in the backyard. Her BF was out of town on a bachelor party. We are fairly open with our sex lives and talk about all the time. She ended telling us how her man in vanilla and will never let her have a threeway. After telling her all the threeways we have done she added in dont forget your mom. I tried acting like we didnt but she said it turned her on and the my husband told her. After a few hours of drinking I decided to skinny dip and convinced my man to aswell. She obviously felt left out and joined us aswell. At this point I loved seeing her huge titties splashing in the water and made my move. We started kissing and eventually worked my way down as he was working on me. I then asked her if it was okay to have a threeway, after saying no she shouldnt it was cheating, told her family doesnt count. At that point my man had his cock in her face and she just started gagging on it. We ended up all getting action and turned me on so much seeing him inside his sister. In the end I got creampied and she ate it out as we then cum kissed. Great night and she cant wait for him to go out of town again!