Doing Sis a Favour

"There may be other ways, big brother, but I've got to know what it's like to have this inside me. To be rent asunder and stuffed full of your flesh." As she said this, she ground that peach of an ass into my lap, her naked buttocks gripping at the loose folds of fabric of my boxers.

And I was lost.

I circled my arms around her waist and pull her to me, cherishing her breasts in my hands through the smooth fabric of the jersey, returning her thrusts with my own. Drilling her naked ass with my boxer clad cock. "There's gonna be hell to pay for this, Lise. But right now, the price seems right." She murmured her celebration of victory, knowing that my resistance was defeated and she would have her wish.

"C'mon Big Brother. Fuck your little sister and make me a woman. Fill me full of the family jizz and make me a baby. Make yourself an uncle-daddy!" As she spoke, she placed her hands over mine and squeezed hard, at the same time pressing that cherry-ripe ass into me and grinding harder.

I kissed my little sister's neck, licked and nibbled at her. Turning her skin to gooseflesh and nuzzling her ear. "You got me sis, I'm gonna pump your cunt so full, you can taste it in your mouth." My hands gripped her jersey and pulled up. As I did, she leaned forward, allowing her golden globes to be unveiled as her top shifted lifted. Not only was this a breathtaking sight but in doing so, that golden flesh ground into my throbbing cock.

"Taste? Now there's an idea." And with that she shifted down the bed and turned until her breath stirred the hairs around my thighs. "Now let's get rid of these pesky things and see if you're as big as I remember." My cock, already stiff gave a further pulse and the fabric covering its tip grew darker with pre-cum, in anticipation. Then my naughty little sister licked that wet spot, one muscle rubbing another as her tongue flattened along its length. Afterwards, she gripped the waistband and tugged. As I wriggled to release my boxers to allow their removal, my penis emerged and bobbed before my sister's face. She watched, mesmerised, following its erratic movements and then swooped, engulfing the swollen tip with her lips.

And she sucked... And she sucked... And she sucked. Her cheeks hollowed in with the pressure. Involuntarily but lustily, I would twitch forward every once in a while, forcing the crown to rub her lips. And I would groan with each ridge and ripple that was mapped by her lips. She slurped back and withdrew my cock form her mouth, to speak,

"You do taste so good Big Brother. So good and tasty. So sweet and salty. But I can hardly get my lips round it, you're making my jaw ache. I best just get this baby maker where it needs to go." And with that, she moved back up the bed, twisting her body and pushing my boxers down to my knees. As she turned around, my newly released drew patterns upon her golden, downy flesh. Tracing her form and inching closer and closer to the cleft of her buttocks.

As we settled into the classic 'spooning' position, she brought my hands around her waist , under her jersey and up to her breasts. Her neck nestled against me an I kissed her, inhaling her perfume and exploring the exposed flesh between shoulder and ear. Content that my hands were where she wanted them, cupping her breasts and thumbing her nipples, her own hand reached between us to grasp my penis.

Gripping it firmly, she rubbed it across her ass cheeks, smearing pre-cum on them, then sliding it between them. Stroking it up and down, we both moaned, groaned and started panting heavily. I squeezed and pushed her breasts as I jerked forwards, searching for a way in. During this, she bent back, thrusting her ass up and down, burying my head between her globes.

"You ready Big Boy?" the words caught as she spoke giving them an erotic edge, pushing more buttons than I thought I had. As she used her other hand to pull at her cheek, I slipped one of mine down and pulled the other, revealing her puckered starfish and sparsely covered pussy. The lips of which were puffed and heavy.

In response I edged forward and she guided me between those lips and into her moist, warm haven. Each inch of penetration escalated the ecstasy of the sensations as her labia stretched around me and her sugar walls moulded to accommodate. If you had asked me yesterday if I would ever commit incest with Lisa, I would have called you a sick fuck and secretly wished that such a thing were possibly. Now a day later, she was sharing my bed and her body as I entered her fertile womb. I had succumbed to her seductions and was prepared to father her child. To impregnate her with my seed and grow life inside her.

And it was wonderful.

Our bodies moved in rhythm and each thrust took me deeper inside. Ultimately, her cheeks rested on my scrotum and I was completely buried inside her. Until this point, we had moved with controlled exploration but once fully impaled, she ground her hips and bent forward. I had to move my hands, smoothing down across her stomach until they gripped her hips.

Once locked, our pace increased and was matched by an increasing temperature as our passions flamed and we lost ourselves the lust of the moment.

The exquisite sensation of penetration, the knowledge of the sin that we were committing, the proximity of our parents and the recognition that it had been some months since I had had this kind of intimacy with a woman all contributed to the rising need to ejaculate.

"Lisa, I..., I ..., I don't know how much longer I can last." I could feel my toes tingling as my body prepared to create life. The world shrank to the size of our bodies, I was aware nothing else but the feel of my cock thrusting into my sister's pussy, my thighs slapping against the backs of hers, my hands sliding on her hips in the sheen of her lust. Her moans rising until she pulled a pillow against her face to muffle the sounds. In a moment of restraint, she pulled her head up to gasp,

"Yes! Yes! I'm so close to cumming too. I need this. Fill me with your spunk. Give me your seed and make me a baby Robbie. Fill my belly and make me a mummy!!!!"

That was it. The flood gates opened and I launched myself into her as her climax hit. Her fists gripped the pillow and her ass thrust back to receive my seed. I was committing the most taboo of acts. I was impregnating my sister with our child. That which had received life from her mother, was giving life to her own child.

And it felt fucking fantastic!

I hadn't felt this good since .... well, I couldn't remember ever feeling this good. Not with my ex-wife or subsequent partners had caused this level of euphoria, of adrenaline rush, of total, total love. It didn't want it to end and I didn't think that it would. I was shooting stream after stream of semen into her spasming womb.

"Oh, Robbie, you're still cumming. Oh my God! I've never felt so full. That was amazing. If I'd known it was gonna be this good, I'd have talked Jeff into letting you fuck me long ago. But all his ideas to get you horny really worked didn't they? His choice of dress for me today pushed all your buttons didn't it?"

In the post-orgasmic glow, the words filtered through to my brain, "Excuse me? Persuade Jeff? Get me horny? Just when did you two plot this?" As I spoke, Lisa curled up and pulled my arms around her.

"Plot's a strong word. But we hatched this a month or so back when our last round of IVF failed to produce any results. Rather than throw more money at it, we thought about a bit of D-I-Y first and to see if you'd help us out. I wanted to just ask you outright because I've seen the way that yo look at me but Jeff wasn't sure and, in his words, he wanted you 'Gagging for it!' and besides we thought it'd be fun to seduce you."

I couldn't believe it, I thought that this was a spur of the moment thing but they'd come up with the idea while stone-cold sober. Not as I thought after an alcohol-fuelled day of risque conversation and banter. "I don't know what to say Lise. I guess you're right that I've wanted you for a while but never done anything about it. All I can say is that while I would have said yes, if you'd asked, this was a whole load more fun so I'm glad Jeff came up with it."

"Me too Big Brother, but hush now. Jeff's gonna come for me in a few hours and I want to fall asleep in your arms for a bit. Who knows? Maybe you'll surprise me later?!!"

And with that, we nestled against each other and drifted off to sleep.