Since she was 10 and I was 11 my sister and I had played with each other.

We grew up in a small 2 bedroom flat with our parents who didn’t have much money and so we shared a room. When our cousins visited we would share a bed and so when I began to get stirrings and discovered sex it seemed natural for me to experiment on her and she did the same to me. We’d tried most things and every time one of us learned about something new we’d tell each other and try it out. Generally she took the lead when the mood took her and I was always willing.

 

On this particular night I was 16 and she was 15. Our Aunt Vicky was visiting with her young son and he was asleep upstairs. Jen and I were babysitting and Aunt Vicky’s chocolate Labrador Bob was on a mat in the kitchen. Mum and dad and Vicky had gone out for a drink and would then go on to the casino until the early hours as the dance hall was free to get in and there was a free buffet to keep the gamblers there.

 

Jen and I sat on the sofa watching one of dad’s porn videos. I had discovered a long time ago that dad had an ever changing supply of porn and Jen and I would often watch them together.

 

This evening it was a compilation of John Holmes shorts and the first showed John teaching a classroom of girls about sex. The girls wore white blouses and short skirts and sat legs open displaying white knickers as John called them up one by one to draw what they thought a penis looked like on the board. After several poor efforts he became annoyed and produced his own monster for them to closely examine and gradually they began to suck him. Within minutes they were all sucking and fucking each other. Jen had stretched out beside me and as John shot his load she opened her dressing gown allowing me to see her naked body. I followed suit and she glanced over at my hard cock pointing skyward.

 

The next film had John arriving in a rear garden where a young naked girl was sunbathing. She explained her dad was out and John began to stroke her tits, she soon had his huge cock in her mouth and he stood astride the sun lounger looking to the patio doors at the rear of the house. Then the camera cut to inside the house looking out and standing at the window watching was a naked teenager clearly masturbating. The camera then went back outside and looking from John’s view point he could be seen through the semi reflective glass stroking himself. Then John called out “Stop watching and come and help me fuck your sister” Jen and I both sat up at that point. The patio door opened and out walked the boy, about 18 years old. He was almost identical to the girl. No doubt they were brother and sister. Jen gasped as he stood next to his sister and she took hold of his handsome cock. “So it’s not just us” she commented. “I didn’t think so” I said. Jen’s hand went to her pussy as she settled back to watch John and the boy fuck his sister. I followed her lead and took hold of my cock and began to stroke it. This incest film really got us going and Jen took my hand and put it on her wet fanny and she took hold of my cock. We both lay back wanking each other and watching. Then in the film John lay on the sun lounger, the sister impaled herself on his monster cock and the brother slipped into her arse. Neither I nor Jen had seen this before. Jen groaned and had a heavy orgasm as the brother sank himself into his sister’s arse. “That looks great” Jen breathed as she stopped shaking. “Bet it hurts” I said. “Not if I relax” she replied.

 

As the men pulled out and emptied themselves onto the girl’s face Jen got up and said she would get a drink. She let her gown fall to the floor and I watched her slim naked body walk away from me towards the kitchen. She left the room and suddenly called out “Quick look at this” I got up and let my gown fall near hers. In the kitchen on his towel Bob the Labrador was licking his cock. The tip was exposed and Jen was staring at it. “Look how big he is, he must be the same size as you but without the knob on the end” she commented.

 

Bob was aware of us and stopped licking. “I wonder what it feels like” she added and walked over to him. She knelt down and talked quietly to him and then ran her hand down his stomach and brushed his cock. I could see her yoyo like pussy open as she crouched. The dog didn’t react so she rubbed his cock with her palm a bit and then took hold of it. “It’s lovely and hot” she said. She began to stroke it and his sheath slid back revealing his thick shiny shaft.

 

“He likes it” she grinned taking hold of his raw meat and stroking it. “Come and stand here and let me compare you two” she ordered. I moved to stand beside her and she took hold of my cock in one hand as she held Bob’s in the other. “They feel the same” she said trying to act like a scientist doing an experiment. “If you get on your hands and knees next to him I can compare you properly.” She beckoned the dog to stand and holding him still using his joystick she directed me to knee down beside him on all fours then looking across underneath us she directed me back and forth a little at a time until we were lined up and announced that we were indeed the same length.

 

Without warning she rolled onto her back and slid under the dog. Looking below me I saw her lift her head and suck his cock into her mouth and began to stroke me. She mumbled approving noises as she sucked the dog and he began to curl his back down to thrust at her. I was getting more excited by the minute.

 

Suddenly she came out from underneath and said “Get him to fuck me.” She got on her knees in front of Bob. He didn’t need any encouragement and leapt onto her back. I took hold of his cock and guided it to her hole, it did feel like mine. A quick probe and he found the mark and clambering up her back he drove himself home. She grunted as he filled her and began to thrust into her.

 

No longer needing permission I stood in front of her and she took my cock into her mouth as Bob drove himself onward. His thrusts shoving her forward. Then she pulled off him and said “Lie down” I did so and she sat astride me. Sahe took my cock into her pussy in one smooth lunge and sank down onto my chest. Bob saw an opening and seizing it got onto her back again. She reached round to direct him and tensed as she guided his cock to her anus. I could feel his cock enter her arse against the underside of my cock through the thin wall that separated her passages. The dog mounted her and she grunted and became tense. We all froze and as she relaxed the dog read the signal and began to fuck her hard. He gripped her sides with his paws and hammered home. I think he was worried she would stop him again.

 

I felt the base of my cock get crushed and realised his knot had built up and he was now locked into her “OH FUCK THAT HURTS” she shouted. “Don’t move or you’ll hurt yourself “I warned “His knot is inside you and he’ll tear you open if you try to pull off, you’ll have to relax and let him finish.” She looked panicked and then we both felt his cock pulse in long slow waves as he began to pour his cum into her arse. It was like being wanked and soon the waves had me cumming. Each wave pulled a small amount of cum out of me and kept me on the plateau of orgasm. This went on for several minutes before he finished and throughout I was in constant orgasm it was incredible.

 

Eventually Bob dismounted and I pulled out leaving Jen on her knees. She sat back and I watched streams of fluid pour our of both her gaping holes. She just knelt there quivering and said that she too had been floating on an orgasm for what seemed like eternity.

 

Needless to say Bob is now a regular part of our fun and I have enjoyed the pleasure of him knotting inside me and streaming hot cum into my arse.