"Oh, fuck yes, Joe! Fuck me!" was accompanied by the sound of the headboard banging against the wall. All Mark could do was lie there. Any chance of sleep at a reasonable hour was long forgotten. At newly 18, he wasn't blind to what his parents were doing. He'd long ago noticed women and their bodies, their sexy curvy bodies. Just the sounds emanating from his parents room had his cock thickening and rising. The light coming through his window, illuminated the tent forming under his blanket. He debated rolling over and cramming the pillow over his head, but he knew that his parents were just getting started and it would be a long, torturous night of raging hard-ons and not sleeping. Reaching down, he firmly gripped his hard cock. It wasn't the longest, but it was fat. The tempo of the headboard banging against the wall and his mother's moans were increasing in volume and frequency. "Fuck, yes! Oh, Joe, fuck. I'm going to cum!" Mark started stroking from the base of his cock to the head, matching his parents' rhythm, wanting to badly cum in time with his mom. Unthinkingly, he imagined it was him fucking his mom, not his dad. He stopped his feverish thrusts into his hand, expecting to be disgusted. Turned off. But his cock was still hard, throbbing and jerking back and forth in search for stimulation. 'No one's gonna know, Mark.' Swearing softly under his breath, he grabbed his cock firmly and started stroking from base to tip. This time, he imagined it was his 19 year old sister he was fucking. His cock jumped in his hand, the image of bending his big assed sister over and fucking her like dad was fucking mom almost made him blow his load.
"Hey Mark..." his sister Shelby said as she walked into his room, cut off by the sight of her not-so baby brother jacking his cock at a frenzied speed. "Uh... Never mind," she exclaimed as she turned to leave. Mark, torn between wanting his sister to see him shoot his load, and decency urging him to cover his jerking cock, gave it one last hurried stroke before covering his throbbing cock with the blanket. "Shit, Shell. I didn't expect..." he trailed off. Nothing could really explain away what she'd just witnessed. "No, no. I'm sorry, I should've waited. I, uh, couldn't sleep with the porn stars going at it." Shelby stood in the doorway to Mark's room, fidgeting. Her arm across her breasts, hand clasped at her elbow as she shuffled her feet. "It's alright, Shell. No harm, no foul." Completely the opposite of what his cock was thinking at the moment. His cock was still twitching under the blanket, beginning to ache. Debating on whether to turn and go back to her room and try to get some sleep, Shelby couldn't ignore her pebbled nipples and the way the slight shifting of her arm across them sent little shockwaves of pleasure to her clit. Her pussy was positively drooling. The sounds of her parents fucking and the sight of that massive dick Mark was failing to hide were causing errant thoughts to run through her head. They weren't close, only a year apart, and they didn't really have anything in common. They were complete opposites. She being a quiet nerd type, complete with glasses and long brown hair which was neatly braided. And him with lean muscles and a basketball player's physique.
"Yeah, sorry Shell. You, uh, caught me just as I was fixing to finish and the sudden stop... It's not a pleasant feeling." Shelby wasn't a prude, she knew about orgasms and sex. But hearing someone mention it caused a deep red blush to stain her cheeks. "Sorry, Mark. I didn't think. I only came in to have some company while the porn stars went at it. "I should go back to my room." Shelby reluctantly stated. Hurrying to leave before anything else happened, Shelby strode quickly from the room and across the hall to her own where she hastily closed the door before frantically tearing her clothes off. Climbing on the bed. She grabbed her favorite vibrator, newly named Mark. Flipped it to the highest setting before quickly sliding it as deep as she could in to her soaking wet pussy. "Oh, fuck me, yes! Oh, Mark!" Moaning with each thrust of the vibrator, wanting it to be her brother's fingers twisting and flicking her hard, sensitive nipples. Shelby rode her vibrator, imagining it was her brother doing all of those things. "Oh, oh oh! Fuck me, oh Mark! As she was cumming, something warm and wet landed on her. Shelby's eyes flashed open to her brother standing in her open doorway, his cock shooting ropes of cum. Their eyes locked, and with some twist of fate a glob of his cum landed on her panting lips. Without thinking, Shelby slipped her glossy pink tongue out to lick up the creamy incestuous treat. Mark slowly walked towards the bed where his sister lay, naked and rosy from her orgasm. He was about to cross a line, his mind wasn't objecting. The only objection coming from his cock as he was taking too long to slide in his sisters wet pussy. "Mark. Shelby whispered, I need you to fuck me. I need to cum, badly." Mark started moving up Shelby's body, this was it, there would be no going back after this. As soon as he slid his cock in her pussy they would be breaking the final taboo barrier. A brother fucking his sister. Mark began rubbing the head of his cock up and down her gash, coating the cockhead in her pussy juice. The feeling was exquisite.
Just as Mark started slowly feeding his cock to her pussy, Shelby told him "Mark. I need you to promise me something. Do not, no matter what I say, cum in me. Ok?" Mark, only half listening and more trying to focus on not blowing his load could only nod his head in the affirmative. "Then fuck your sister's pussy, baby brother." Without further ado, Mark slid his cock in one thrust until his balls were flush against Shelby's ass. "Oooh, fuck. You're huge!" Shelby groaned. The brother and sister had done it. His bare cock was seated deep in his sisters clenching pussy. His sister's pussy was tight, almost painfully tight. Each clench of her pussy gripped him tightly and if he didn't focus he would cum before either of them were ready. Raising her knees to her chest, Shelby opened her pussy to give her brother deeper access. Allowing Mark to hit her clit and g-spot at the same time. Mark slowly drew back his hips, leaving on the tip in before sliding back in to his sisters pussy. "Oh, fuck your pussy feels so fucking good Shell, fuck."
"Oh, fuck, Mark. Fuck me. Forget what I said earlier, I want you to cum in me. I want to cum on your fat cock as you're cumming in my pussy." Thrusting faster and deeper, Mark reached between them and started rubbing Shelbys clit. He wanted her to cum on his cock and he wasn't going to last much longer. Forgetting entirely the need to be quiet, the siblings started fucking with wild abandon. Mark, thrusting his fat cock in to his sisters creamy pussy, both moaning together. Shelby, pinching and pulling her nipples, with little pulses hitting her clit. Amplifying the feel of Mark rubbing her clit and his cock hitting her g-spot. "Oh, fuck Shell. I'm going to cum all in that nice little pussy, baby." Just the words alone pushed Shelby to the brink. Knowing that her body was going to make him cum. "Ah! Fuck, yes Mark. I'm going to cum on that fat cock. Fuck-fuck-fuck!" Shelby's body drew tight as her pussy gripped onto Mark's cock, clenching him for all he was worth. With one final thrust, Mark started spurting his cum deep in his sisters pussy as she came all over his cock. The clench and pull was almost enough to get him horny again. With the final contraction from Shelby's pussy on his cock, Mark collapsed on his sister.
Satisfied, Shelby practically purred. She had never been so thoroughly fucked in her life. This may become her new favorite past time. "Mmm, Mark. That was amazing. You're the best fuck I've ever had. Do you want to finish in my mouth?"
"Huh?" was all Mark could say, "did you want me to suck you off?" replied Shelby. "What? I came already."
"What? Where?!" Shelby stated, starting to panic. "You told me to cum in you. That you wanted to cum on my cock as I was cumming in you."
"Oh no, fuck. Mark, I'm not on the pill! I told you not to listen to me at the start, I know me and I love having a guy cum in me. It makes me cum harder. Fuck!!"
"Oh, shit." was the only thing Mark could reply with. That and a hardening cock. "Well, we'll get the morning after pill tomorrow. Since the damage is done, I'm not done fucking that pussy full of my cum, Sis."
"Oh. Fuck. That was hot. Who would have thought baby brother had a dominant side?" With a long stroke, Mark started sliding in and out of his sisters cum filled pussy again. For a night of breaking boundaries, it was going to be a long and satisfying one.