As I woke up, I knew there was something unusual. The room I was in was my own room, and so was my bed, but I was not alone. In my arms was my younger sister, still sleeping. She was completely naked, and so was I. I felt a dull ache in my balls, and the hair in my crotch was all matted together. Slowly it came back to me what had happened last night, how Marlene and I had fucked like animals for hours until we both were completely drained. As I felt my tired cock swell again between my sister’s legs, I thought about how things ever could have culminated in last night’s bout of passionate lovemaking. It was a long story, starting years ago, when we were just little kids.