Our parents worked late. My hot, seventeen-year-old sister, a real tease to my friends, was in my sex fantasies. I was fifteen, super horny and happened to sport a big, nine-inch cock. I jacked three to four times a day. (Oh, to be young.) Seeing her parade around the house in just her thong panties and midriff tee-shirt was more than a young teen could handle--even if she was my sister. I will detail how I found myself crossing the line, doing things no parent should know about.