I've always been there for Susan since she was a kid. I'm 12 years older than her and once her mother died I was all she had most of the time as our D...ad traveled a lot. I had also been there for Caitlyn since she was born and had been more of a father to her than her real dad. The last two years I had not been able to see them as much as I wanted since my new job had crazy hours. In fact, this was the first Saturday I’d had off in a while. I heard the front door close and turned to see Caitlyn. " She smiled. I smiled back. OK, what now?She said "Have a seat," motioning me back to my narrow little hard back chair. Sitting down did nothing to disguise my condition. "I'm sure if we just wait, that ole hard-on will go away and then you can model the shorts for me again." This could be a long wait," I said. As I sat there staring at her, she stepped directly in front of me and cast her eyes down at my groin. Yeah, this could take a long time, I thought.She stood facing me while holding her. . .”I let go of her ass and tits and Nancy turned around. She rid herself of her dress and panties and while she knelt before me I carefully positioned my rock-hard pole against her rectum. “Come on, shove it in,” she yelled and I let go of my reluctance. Without further thinking I pushed my cock in her arse. To my surprise my prick slid in quite effortlessly, even though it felt incredibly tight. I found the experience enormously exciting and stated to knead her buttocks again with my hands. I stuck the panties into my mouth to savour the juices, put the picture on the floor and started stoking my cock hard and fast. I was just about to come when the toilet door open and I looked up it was my aunt, my moms sister. She looked at me seeing my fully erect cock and I started to shoot my thick sticky cum all over. She said sorry and closed the door. I was still cumming and the panties were still in my mouth. When I finished cumming I realised what had just happened. I was so.