"So ya wanna fuck?" the twenty-three year old redhead asked me as she stood in the doorway of my room and smiled.
"Sure Mary," was my response. I threw back the covers of the bed on which I was laying. This exposed my hardening cock.
"Let me just go put Dan Jr. to bed and I'll be right back."
She left and went to put our four month old son in his crib and tucked him in for the night. Five minutes later she walked into back into the bedroom completely naked. My hard dick was already waiting for her. She came up to the bed and straddled me facing forward. The opening of her vagina was at the head of my dick. She slowly slid down. When our pubes meshed she let out a moan.
Then she said, "you fill me up so good bro. Are you going to give me another baby?"
"I have almost a months worth of sperm saved for you."
"I'll definitely be getting pregnant again."
"Yes, I'll give you as many babies as you want, sis."
"Hopefully we'll have a girl this time."
"If not, we can try again, next year."
"How about we try to have a baby once a year for the next six years or so?"
"That's at least seven children, sis."
"I know but I liked that you got me pregnant, and now I want more."
The first time Mary and I had fucked was just after my nineteenth birthday, a little over a year and a half ago. I was visiting her for the summer and staying in the spare bedroom of her apartment. One Friday evening she came to the door of my room and asked, "Dan, have you ever thought about me in a non-sisterly way?"
What do you mean Mary?"
"I'm asking have you ever had a fantasy about fucking me?"
"To be completely honest sis. Yes, I have fantasized about fucking you, many times. Why?"
"Oh, just curious."
"You had to have had a reason for asking me this question. Out with it."
"I heard you jerking off last night, and it made me realize that I am very horny."
"Ah-ha."
"So would you fuck me right now if I was willing to let you?"
"Damn right I would, sis."
"How about it, ya wanna fuck me?"
I answered, "Sure but only under three conditions."
"What are those conditions," asked Mary"
"First of all I don't have to use a condom. Second, I get to shoot all of my sperm inside of you. Lastly, this will be an ongoing thing. We will fuck at least three nights a week."
"I'm not sure if I like conditions one and two, but number three I can agree to."
"If you want my dick in your pussy you're going to have to take my cum as well."
"You could use a condom, please."
"No that point is nonnegotiable."
"What would you say if I told you I don't use any form of birth control?"
"You're not on birth control?"
"Yep. So does that change your mind. Do you still want to shoot your sperm inside your possibly fertile sister and make a baby with her?"
"I told you Mary. If I fuck you I am going to cum inside of you."
"You'd impregnate your own sister?"
"If she wanted me to fuck her, I definitely would."
Mary stood at the door for a second before she walked the rest of the way into my room and then unbuttoned her blouse.
"Okay, Dan, I'll let you fuck me and cum inside of me. I'm too goddamned horny to go another night without a fuck, even if I have to fuck my brother, let him shoot his sperm inside of me and possibly impregnate me."
She stood at the foot of the bed and unzipped her skirt. Mary was now only wearing her stockings, panties and bra. She then removed her bra and tossed it to me. I caught it and tucked it under my pillow. I took a look at her nicely proportioned 32C tits. Mary then slid her panties down her legs exposing her shaved pussy to my eyes for the first time. When her panties hit her feet she kicked them at me. I caught them as well and they quickly joined her bra under my pillow.
"Aren't you going to invite me to join you in bed?," she asked.
For a response I flipped back the covers and she got to see my 7 inch erect cock for the first time. Mary slowly climbed into the bed with me. Our lips met tentatively at first and then we became involved in a very passionate kiss. Meanwhile I maneuvered my dick to her pussy and touched the head of it to her entrance. Mary gasped as she felt the contact. I began to push and I felt my cock begin to sink into her depths. Slowly my dick made its way all of the way into her vagina. My balls slapped against her pussy lips.
"I can't believe I'm letting my brother fuck me," she whispered but loud enough for me to hear.