I managed to get Cheryl over to my couch and I fell on top of her. Our cocks were having a sword fight now. Then Cheryl whispered in my ear."Suck my c...ck please, Tom"I was a little shocked to be honest. I had never taken a cock in my mouth before. If I didn't suck on Cheryl's dick, would the sex stop right there? I moved down between her thighs and lifted her dick in my hand. I lowered my lips around the tip of her shaft and began to suck on head. Cheryl was moaning and running her fingers. I pulled the rope tight then tied it off. When I went back to work on her legs, she tried to move but the ropes bit into her sensitive underarms and she had to work twice as hard to keep still.After twenty minute of that, her legs were on fire and she was hanging silent, limp as a side of beef. I went into the kitchen and got a cold beer, drank a few mouthfuls while we watched her hang there. "Anybody want to fuck her yet?" I asked. There were no takers so I went back to work.I still wanted to. . . . I want you to show me. I want you to do it again." "Whoao, sis! Now let's think this over. What about all your sensible rectitude about privacy and all?" Fuck privacy. I've been thinking about this since before we went to bed. Fuck thinking about it anymore." Without his realizing it, she had gotten a grip of his bed clothes and she was able to pull them back quickly to expose his uncovered nudity. Whatever reservations he had rationally about acceding to her. But the most interesting thing to happen that night was about to come, after what seemed to be an hour of lying there quietly thinking, I turned to my sister who was squirming a lot on her bed and there I saw her… she was playing with herself! I stared a her with surprise as she moaned softly she had before, but this time I kept quiet and didn’t say anything. That’s when I began to imitate her, only without the moans. It began to feel good but then she stopped all of a sudden.