If you've read part one, you'll know where we are.! Now I was seventeen, my sister three years younger. It was a Sunday, and we were both home from boarding school. Sis had brought a friend back from her girls' school, and we pretty much kept to ourselves. About midday, I sauntered into the titchen, and Mum asked me to tell Sis that lunch would be at 1.00. Without thinking, I went upstairs and walked into Sis' room without knocking... The two girls were lying on the bed, naked from the waist down. Sis had a recorder [flute-like musical instrument] in her hand. I backed out, embarrassed, murmering "Lunch will be ready at one", and closed the door. Then I thought about it. I could hear giggles from within. Silently I eased the door open again and peeked round it... Sis was using the recorder to masturbate her girlfriend... I watched for what seemed like ages... Sis's dark haired friend writhe in pleasure. I could stand it no longer, and slowly entered the room, unzipping my trousers and pulling out my hard cock. The first they realised, was when I placed my cock on Sis's bum. She whirled round in fright, then seemed to relax when saw it was me. "don't let me stop you!" was all I could think of to say... But stopped in their tracks they were! They lay there together; two cute pussies... The other girl was now fingering her clit, and my hand joined hers, allowing her to guide me.... Meanwhile, Sis took hold of my cock, and guided it into her. "you sure about this?" I asked. "feels better than a recorder!" she answered ... And she felt SOO good too! Her tight pussy gripped me and she rubbed her clit against me... Then I felt her girlfriend rubbing herself against the back of my thigh... I slipped out of Sis, and rolled onto my back... The cute dark-haired girl immediately came astride me, rubbing my cock against her. I wanted to slide into her, but it was clear she was a virgin... I pressed against her, and was suddenly inside her. She was all wet and slippery gorgeously so, and I knew I had to come out before the inevitable happened. I pulled out just in time, squirting a huge stream of semen over both girls..... Lunch was on the dot of one.