We'd talked about experimenting with others before. My GF had a friend she'd made out with before and who'd had threesomes previously, so we thought she'd be good to start with. We both know her, so it'd be less awkward. I was over at a mate watching some football while my GF and her friend were at home having a girls' night. Then I got the text. "Come home if you want some fun." I got home as soon as I could. Walked in and my GF gestured to sit between the two of them. As soon as I did, they ma...