My girlfriends little sister (Sue) visited and stayed with us over a weekend once every month. At nineteen she was pocket rocket version of her older sister, shorter with a more athletic build. Ann my girlfriend always teased me that Sue was desperate to sleep with me. She also said that she knew how attractive I found her. I admitted to Ann and myself that I did find her gorgeous body and her vivacious character very appealing.
The three of us would often watch a film together late on the Saturday evenings. As often as not Ann would fall asleep halfway through the film and I would have to wake her to take her to bed. It was a hot night that Saturday. As usual we had showered and got dressed for bed before settling to watch the film. We all sat on the huge sofa with Sue in the middle watching a very ordinary film. Ann was slumped with her eyes closed within minutes of the film starting. Sue was dressed in one of my old shirts with buttons down the front. She constantly fiddled with the shirt and it took me a while to realize that I could see more of her boobs including the hint of hard nipples.
Increasingly, she would look at me with a smile that seemed to offer so much. It was not until that holding my gaze she reached into the shirt and started to play with her nipples that I began to panic. Her smile encouraged me to look down at her nipples that looked surprisingly large and very erect. I found it hard to take my eyes off them, but with a quick check on Ann I indicated to Sue that she had to stop what she was doing. This only seemed to encourage her to play harder and rougher.
Then she reached across and took one of my hands and tried to guide it to her left nipple. I snatched my hand away and tried to make it very clear that she had to stop. Looking towards her sister she very quietly knelt up facing the back of the sofa. She then moved across so she was straddling my right leg. I went to stop her but realized that I could not do this without threatening to wake Ann. With a wicked smile Sue put her finger to her mouth as if to quieten me. She pulled the shirt up slightly and I felt the warmth of her groin on my bare leg.
When she leant towards me she slid down my leg and I felt not only the warmth but also how wet she was. Her face was right in front of mine as she slid up and down my leg. Her smile was replaced by a slightly dazed look, as it was clear that she was arousing her pussy and clit from the friction with my leg. I dare not move as she carried on rubbing for a minute or two. When she moved to rub against my knee I knew she intended to orgasm on my leg. She now brought her hand down and stroked my erection through my shorts. I had not even registered that I had an erection but it was full on.
Sue was now grinding her pussy and clit hard against my boney knee. I sensed her urgency growing just before she whispered in my ear that she was going to have a huge orgasm. It was this that did for me and I knew I would explode any second. I was petrified that we would wake Ann or that I would make a huge mess. Sue might have been on verge but what she did now shocked me. She pulled the waistband of my shorts out and engulfed just the head of my cock in her warm mouth. I hardly had time to enjoy either the sight or the feel of this as I erupted with a force rarely experienced. She rode my knee as her body was racked with spasm after spasm. She made no sound only the squelching of her wet pussy on my knee.
After what seemed like a very long orgasm she slumped with her mouth still around my fast deflating prick. She had managed not to spill a drop and with apparent reluctance rolled off me and in the process disturbed her sister. The film was just ending and Ann asked whether we had enjoyed it. We both said the film was not good but we had enjoyed it. I was afraid that Ann would sense what had gone on from the smile on Sue's face but she seemed oblivious.
We were soon in bed and Ann found my cock with her hand. I was surprised that having had such a strong orgasm minutes before my prick was soon expanding in her expert hands.
"I am so pleased that my little sister has not completely satisfied you my dear."
I didn't know what to say, as I wasn't sure what she had seen.
"Don't worry, you seemed to resist her for much longer than anyone could reasonably expect. I did wonder whether she would try and fuck you right there. She said this morning that she had not had any action for a long time so I thought I would give her a chance to get some at least tonight."
