It was perfect. I was going to be my sister's date and if I played my cards right I would fuck her without her knowing.Before I even had time to reall... think through the semantics of the plan or decide whether this was a good or bad idea, Wendy walked out in only a towel, not feeling remotely strange to be almost naked in front of her brother, and snapped, "Why the fuck do you have my phone?"I said, annoyed as usual by her bitchy attitude, "Your boyfriend called and I figured you would want me. Not…now! She told herself over and over, trying to ignore the small, pathetic-sounding voice within, which kept replying, “But when?”It was when that small voice became too loud to completely ignore any longer that Marcia had started to buy lingerie. At first it had been unconscious—replacing her plain, worn-out underthings, one at a time, with something just a little bit fancier or more colorful. But over time it became the way she rewarded herself for any small success, or after a hard week. I could feel her beginning to move her arse with small jerks while her breath was very irregular. Then she started moaning and grunting as I speeded up my plunges. Her body began jerking and I thought she was choking the way she was gasping for air.I asked her, “Are you alright Mum?”. She didn’t answer as her body was still jerking. With my cock buried deep in her hairy pussy, I started shooting cum in her for the second time.We soon relaxed and she opened her eyes. She said, “Hand me some. ”“Oh no Mistress … Mrs. Parrington. I wouldn’t feel right about that, not yet, anyway.”“All right David. David, do you have a girlfriend?”“Yes Mrs. Parrington, I’m dating Dinah Gordon.”“I see. And are you two sexually active?”David blushed a bit, it was actually cute, and then he looked up. “Yes Mrs. Parrington, for a few months now.”“Is she cute?”“Pardon me?”“You heard me, is she cute?”“Yes Mrs. Parrington, she’s very pretty.”“Now David, listen to me, because this is very important … do.