Even as my hand was throwing, Crista’s fingers were unbuttoning and unzipping my jeans. Slick as a whistle, she slipped them and my briefs down over...my hips and down my legs. The girl dropped the clothing over the side. Naked at last! My cutie-pie 13-year-old sis and her 17-year-old brother were preparing to become lovers! Despite the forbidden proprieties, we two were ecstatically happy. One look at my swollen erection might give the impression this was all about sex. A look a Crista’s. .. I mean you didn't hurt me or anything ... You're ..." she stopped herself. She had been about to say "You're big and it felt wonderful."They took a short break and Lori handed out more towels. While they rested Mark's erection flagged. He'd been up for more than an hour, so it wasn't unusual for him to lose his hardon. When it was time to resume the poses Lori stood up and went toward Mark. "Let me help with that," she said, a sort of hunger in her voice. "I mean we can't ask your sister to. S. was still washing dishes, her back to the kitchen door. Silently, I crept up behind her until I was a foot or two away. Then, I walked up behind her and put one hand on the sink edge on either side of her, trapping her. I leaned in, over her shoulder, my crotch tight against her full ass."Lenny!" She almost shouted as I moved my body into place. "What are you doing?"She tried to back up, but I held her in place. I squeezed her between my forearms and leaned in to whisper in her ear."You. I was very aroused and I was tempted to let him fuck me if he tried. His thumb was rubbing my clit while he fingered my pussy. He made me cum. I threw my head back, moaning and shaking. Maybe I would have let him fuck me. I’ll never know because after my climax he said he needed to be repaid and wanted me to suck him off.I knew he expected me to do it because I had done it when we went out in Austin over Christmas. I didn’t mind so I said yes and unbuckled his belt. I unbuttoned his pants and.