Same with me. I've had sex many times in the same room with my sister and her boyfriend and me and mine. I love to watch her lay on her back with her legs pulled up to her chest while her guy thrusts his beautiful dick in and out of her pussy-sometimes she'll lift her head up and admire it and touch it, shining with her juices, as it goes in and out of her belly-we'll look over at each other as we fuck our men, and I'm sure she wonders what my guy's dick would fell like if it filled up her belly-we egg each other on with our noises, and sometimes if one of us starts to come, it'll set the rest of us off-kind of an orgasm chain-sometimes when my orgasm starts my sister will hold my hand tight or stroke my hair until it's completely over and I catch my breath. A lot of times our guys will pull out and let those white ropes of jism out on our bellies at about the same time-sexy to see those two swollen members cough up that beautiful man-spunk together. We're just not kinky enough to swap partners or do a threesome thing, but I'm sure those thoughts go through everybody's mind, though.