I nodded.“Jamie. Why would that make me mad? Everybody does it. It's absolutely normal you know. If anything you should be mad at me for not knockin....”“Everybody does it?” I asked. I couldn't believe I was discussing this, but the idea that I wasn't a pervert as my mother would have me believe was quite a relief.She nodded.“But just boys, right? Girls can't...uh...don't...uh...have...uh...”“Penises?” She said helpfully. Smiling, she explained, “No, we don't have penises, but we do have other. For a few seconds, I was mortified that my older sister could feel my boner pressing onto her soft lower belly. But, since she didn’t pull away, I thought to pull a slight prank or something, so I just flexed my ass muscles and arched my back a bit pushing my boner into her flesh thru our clothes.She didn’t seem phased. She didn’t pull back a millimetre.It felt very good. While I wasn’t a virgin, my sex life at fifteen was anything but busy.Since she didn’t pull away, I figured she doesn’t mind. She nods“Down on all fours, then come over”She obeys, dropping to her knees and then forward onto her hands. All the while with the blindfold on she can’t see anything, just going by the sound of my voice. She slowly crawls forward her lovely pert ass in the air. I imagine pulling those tiny little panties down and sticking the head of my cock into her very tight, little butt-crack! But I refrain, instead I lean over and give her ass cheeks a firm spank. She gasps. I reach over and spank again.. "From behind, that could be Jodie" he thought. Chriscontinued to roll up stockings and attach them to the matching garterset before finally hooking up the bra. "He's done this more than once"Kyle noticed. "Right, ok your turn, what do you think?," he turned roundand twirled for the other boy. "You look like your sister" was all Kylecould respond. "Okay... lets do you?" Chris answered.Five minutes later both boys were sat on the carpeted bedroom floor,while Chris using a vanity mirror began.