Two dys ago I caught and watched my seventeen year sister fucking her boyfriend. She was sat naked on his cock when I walked past her open bedroom door. Looking round when I'd been watching for about five minutes, she looked directly at, licked her middle finger and slipped it up her asshole, whilst still her boyfriend. Smiling at me as I walked away to whack one off in my bedroom.
Yesterday she asked me if I liked what I saw as we sat in the lounge across from one another. Before I could answer, she spread her legs in her short skirt and showed me she wasn't wearing any panties. Her pussy looked so good, and so wet. Again smiling at me, my little sister got up flipped up her skirt to flash me her butt and went to her room. Only later on did she approach me and ask me why i didn't follow her.
Now I'm wondering if my little sister wants me to fuck her. And if she does, being my sister, should I ???