Hopefully, without you getting mad, getting too embarrassed, or you saying 'bite me.'"'Bite me' was her phrase du jour lately. She said it so often th...t I'd considered actually biting her more than once."What?" she snapped. There'd been a lot of snapping the last six months or so, since just before she'd turned thirteen. That was the reason we were having this conversation.I swiveled my chair back to the table and looked down at her math book. "Let's try problem six." The reason her mom had. "I nodded my head slowly. "Yeah, I can see where that came from. Dad was always bragging to us that having twins proved he was a real man. He said that no real man needed anything other than what God gave him. Tom and I really ate that up when we were kids. If the situation was reversed, I don't know if I could go through with something like artificial insemination either. Not and keep my self-esteem. But that doesn't mean he's suicidal. Maybe depressed, but never suicidal."She tensed up, and I. ”I was just speechless. On the one hand, I found it exciting to be part of this foursome, and I even thought it would be so arousing to see my sister being fucked in front of me. I mean, some weeks ago, I had seen her fucking my cousin, something I just couldn’t stand, but this was going to be different. I just didn’t want people to know what was going on between us, so I really hoped Matt and Joanna could keep this secret.We also talked about creating the right mood for that special night,. My cock jerked again in my briefs, eager to get out."It really doesn't look too comfortable in there" she laughed "Shall we let it out!" It does feel rather strained to say the least" I replied, "Sure, we might as well get a good tan all over"She stepped across, her boobs vibrating gently and knelt down in front of me. "Come on then, out you come young fellow" and she carefully eased down the waistband, over the throbbing bulge. My cock leapt out, hard and straight, waving in the open air; Liz.