So there I was, naked on my bed, with dad's huge cock jammed up tight inside me, and mom walks in the door. There was a moment when dad and I froze, both expecting some kind of outburst, but when it didn't come and mom instead indicated that she'd been listening to us fucking for quite some time, I felt dad relax, but he still shocked me by inviting mom to join us, and she shocked me even more by slipping off her robe and walking naked over to the bed with the hottest, horniest smile on her face that I'd ever seen.
As she came close to the bed, dad started to slide his cock from my pussy, and I groaned in disappointment, "Don't worry, honey, I'll be back, but I think your mom needs this more right now"
"I sure do" said mom "hearing you two fucking has turned me on like never before"
She slid onto the bed, and immediately dad started sucking and licking on her large, firm tits, and she started moaning in pleasure. Wow, I'd never watched anyone getting it on before, especially not my parents, so I moved back a little to observe better. It wasn't long before dad was sliding his cock into mom's welcoming pussy and she was shivering and shuddering like crazy, but immediately I noticed that she was holding back and dad was holding back too, and I could see why, dad's cock was only about three quarters deep into her pussy, and he was having to take things very gently. But obviously, over the years they'd learned to accept that and it wasn't long before both of them were yelling out as they brought each other to a massive climax. Then I learned something new about myself, watching them fuck had really, really turned me on! my pussy was on fire and just dying to feel dad's massive cock in it again.
But I had to wait a while, and as I waited dad told mom how it had all come about that he was in bed fucking me, and how much he wanted to fuck me again. Mom just grinned and turned to me "So, you decided to get your sex education with Derek, I'm glad, I like him a lot and I'm sure he looked after you real good"
"Oh yes, mom, he's been fantastic - then a sudden thought came into my head and I decided to take a risk - he's not as big as daddy, but he does have an absolutely beautiful cock, and he sure knows how to use it!"
I saw an immediate flicker of interest in mom's eyes, and I'm sure dad saw it too, as he grinned widely, "Well Elsie, what do you think? you've always had a problem with my size, and you know it's been one of my favorite fantasies to see you with someone else, why don't we invite Derek over for a foursome?"
Mom blushed! yes, she actually blushed, "Oh I don't know if I could, I mean I've never, I mean Derek's with Ruthy at the moment, I mean I don't know how, oh Jack, I don't know what I mean!"
Dad's grin widened even more, "Elsie, you've been saying for months what a good looking man Derek is and isn't it a shame that he hasn't got a woman in his life, can you look me in the eye and tell me honestly that you've never once thought what it would be like to make it with him, fantasized about having sex with him?"
Mom's face got even redder and she couldn't look dad in the eye, so we both knew what the answer was, then dad turned to me, "Well Ruth, I guess at the moment Derek's your man, so how do you feel about your mom having sex with him, and how do you think he'll react?"
I thought for a moment, trying to imagine the scene in my mind, and it turned me on like crazy! me with dad and Derek with mom, Wow! "Derek is horny, very. very horny, and I'd think he'd take one look at mom's gorgeous body and start to drool, but it mightn't be easy to move things on from there - I laughed - I certainly found it hard to seduce him! but as for my feelings, as long as we get to swap around and mom and I both get to taste both of you, I would love it to happen!"