sis x sis x step-dad - fucking behind mom's back | sister threesome story

The front door creaked open, revealing two 19-year-old sisters, Sarah and Emily, both with flushed faces from the summer heat. They had decided to cut their day at the beach short, eager to escape the scorching sun. As they made their way through the hallway, they heard muffled moans coming from the living room. Intrigued and slightly unnerved, they slowly approached the source of the sound.

As they peered around the corner, their eyes widened in shock. There, sprawled out on the couch, were their mother, Linda, and their stepfather, Mark. Their bodies were entwined, sweaty skin pressed against each other as they moved together in a rhythmic dance of pleasure. Without missing a beat, Mark glanced over at the girls and quickly disentangled himself from Linda, throwing a blanket haphazardly over their still heaving forms.

"Oh! Girls, you're back early," Linda stammered, her voice shaking slightly as she tried to compose herself. "We didn't expect you for hours!" She looked nervously at Mark before standing up and smoothing down her wrinkled blouse.

Mark cleared his throat and adjusted his pants, trying to regain some semblance of dignity. "Yes, yes, welcome home, ladies." He forced a smile, but it didn't quite reach his eyes.

Sarah and Emily exchanged uneasy glances before making their way to their shared bedroom. Once inside, they closed the door behind them and stared at each other in silence for a moment. Finally, Sarah broke the tension.

"Did you see what I just saw?" Her voice was low, almost a whisper.

Emily nodded mutely, unable to tear her gaze away from her sister's face.

Sarah took a deep breath and let it out slowly. "Honestly? That was kind of...fucking hot."

Emily's mouth dropped open, and she blinked rapidly. "What? Are you serious right now?"

A slow grin spread across Sarah's face. "Absolutely. I mean, come on, they're our parents—it's not like we can actually do anything about it. But watching them lose control like that? It's exhilarating."

She began to strip off her bathing suit top, exposing small, perky breasts with tight pink nipples. She cupped them in her hands, teasing the sensitive peaks with her thumbs. "Don't tell me you weren't getting turned on by all those moans and gasps," she challenged, her voice husky.

Emily hesitated for only a moment before giving in to curiosity and desire. She slipped out of her own swimsuit, letting it fall to the floor in a damp heap. Her body was leaner than Sarah's, with larger breasts and wider hips. She lay back on the bed, spreading her legs wide apart.

"Fine, maybe I was a little bit turned on," Emily admitted grudgingly. She reached down between her thighs, finding her clit already swollen and tender. She started to circle it gently, shivering as waves of pleasure washed over her.

Sarah's grin widened as she watched Emily succumb to her desires. She climbed onto the bed beside her sister, mirroring her position with legs splayed open. Together, they touched themselves, lost in the growing storm of pleasure building between them.

As their breathing quickened, Sarah spoke up, her voice barely above a whisper. "Can you imagine what it must feel like for Mom? To have that huge cock buried deep inside her, filling her up completely?"

Emily whimpered softly, nodding her head in response. She imagined the weight of Mark's body pressing down upon Linda's big tits, the feeling of him driving himself relentlessly into her willing flesh. The thought alone brought her closer to the brink of release.

Sarah continued, her words painting vivid images in Emily's mind. "Does she scream his name when he makes her cum? Does she beg for more?"

Emily could hardly think straight anymore. Every nerve ending seemed to hum with energy, drawing her steadily towards climax. Her fingers moved faster, desperate to find sweet relief.

"And Dad...does he love hearing Mom cry out in pleasure? Does it make him harder knowing that he's the one bringing her to the edge?"

At these dirty words, Emily finally crossed the threshold, crying out as waves of pure ecstasy crashed over her. Her entire body shook with the intensity of her orgasm, leaving her breathless and spent.

Not far behind, Sarah followed suit, her own release rippling through her body like thunderous applause. She collapsed onto the mattress beside Emily, utterly drained yet somehow invigorated by the illicit encounter.

They lay there side by side, hearts racing and lungs burning from the exertion. After several moments passed, Sarah rolled onto her elbow, propping herself up to look directly into Emily's half-lidded gaze.

"That was incredible," Sarah murmured, a satisfied smile playing at the corners of her mouth.

Emily nodded weakly, still struggling to catch her breath. "It was definitely...something else."

Sarah couldn't resist the urge to bridge the gap between them. She wrapped her arms around Emily, pulling their naked bodies flush against each other. The warmth of their skin sent shivers down Sarah's spine as she allowed herself to fully embrace this new connection with her sister.

Inhaling deeply, she whispered into Emily's ear, "I need to feel Mark's cock inside me."

Emily tensed at the unexpected admission, but Sarah didn't pull away. Instead, she held Emily tighter, waiting for her reaction.

When Emily eventually spoke, her voice wavered slightly. "But he's our stepfather...that's wrong, isn't it?"

Sarah shrugged nonchalantly, tracing idle patterns on Emily's shoulder blade. "Maybe," she conceded, "but that doesn't change how I feel. Does it change how you felt while watching them earlier?"

There was a pause before Emily answered hesitantly, "No, I suppose it doesn't."

Encouraged by her sister's response, Sarah pressed on. "Then why should we deny ourselves the pleasure? We're adults now, Em. We can make our own decisions."

Emily considered this for a moment before sighing resignedly. "So, what do we do now?"

Sarah smiled deviously, her eyes gleaming with determination. "Now, we take matters into our own hands."

Sarah couldn't resist the temptation any longer. She captured Emily's lips in a passionate kiss, pouring all her pent-up desires into the exchange. Her tongue probed hungrily at Emily's mouth, demanding entry which was readily granted.

Breaking away from the kiss, Sarah grinned mischievously and announced, "The plan starts today, while Mom is out shopping." She jumped off the bed and headed towards their shared closet, rummaging through hangers until she found what she was looking for.

Excitedly, she pulled out two skimpy outfits - tiny crop tops paired with high-waisted shorts that left little to the imagination. She tossed one set at Emily, who caught it reflexively, eyebrows shooting up in surprise.

"Are you suggesting we dress like sluts and try to seduce Mark?" Emily asked incredulously, even as her heart rate spiked at the prospect.

Sarah chuckled, shrugging sheepishly. "Well, when you put it that way, it sounds so crude. But yes, essentially, that's the idea."

Emily eyed the outfit skeptically but ultimately gave in to the thrill of the proposition. If she was being honest with herself, she'd admit that the idea excited her more than she cared to acknowledge.

Allowing herself a small smile, Emily responded, "Alright, let's do it."

Over the course of the afternoon, the sisters prepared themselves for their audacious mission. They curled their hair, applied makeup liberally, and squeezed themselves into the provocative attire Sarah had chosen. By the time they finished, they looked like carbon copies of one another - only difference being their varying hairstyles.

As they admired their reflection in the mirror, Sarah linked her arm through Emily's, squeezing reassuringly. "Remember, Em," she began, her voice steady and confident, "this is just a game. No matter what happens, we stick together and support each other."

Emily nodded earnestly, meeting Sarah's gaze in the mirror. "Got it," she agreed, swallowing hard against the knot forming in her throat.

Emily mustered up her courage and initiated the next phase of their daring plan. She sauntered over to where Mark sat awkwardly on the couch, attempting to maintain some semblance of composure despite the obvious discomfort written all over his face.

Clearing her throat lightly, Emily purred suggestively, "I bet Mom was having so much fun this morning."

Mark's eyes widened in alarm, and he scrambled to stand up, only to find himself trapped between the coffee table and Sarah, who had materialized seemingly out of nowhere. Before he could protest, Sarah reached out and grabbed hold of Mark's bulging erection through his trousers, leaning in close to whisper seductively,

"We need whatever mom was having this morning."

Mark gaped at them, speechless and paralyzed with shock. His brain struggled to reconcile the scene unfolding before him - his teenage stepsisters, dressed provocatively, openly propositioning him for sex. It was a fantasy he had often entertained privately but never dared to hope would become reality.

Sarah wasted no time asserting dominance over the situation, pushing him roughly onto the couch and straddling his waist. She ground herself against his rock-hard erection, eliciting a low moan from deep within his chest.

Emily, equally entranced by the debauchery unfolding before her, began working diligently at freeing Mark from the constraints of his clothing. With nimble fingers, she unbuttoned his shirt, revealing a toned torso covered in a light dusting of hair. She ran her hands over the firm muscles, marveling at the strength contained within.

Mark's head lolled back against the cushions, eyes closed as he surrendered to the dizzying array of sensations coursing through his veins. The feel of Sarah's slick folds sliding against his shaft, coupled with Emily's gentle caresses, proved nearly too much for him to handle.

Heavens above, he mused silently, had he died and gone to heaven? This was surely sinful behavior, deserving of eternal damnation. Yet, even as guilt gnawed at the edges of his conscience, he couldn't bring himself to care. Not when faced with such earthly delights as these beautiful young women eagerly bestowed upon him

Sarah took things a step further.

With surprising strength, she gripped the waistband of his trousers and yanked them downwards, freeing his engorged manhood from its confines. Gasping slightly at the sight, Emily couldn't help but appreciate the beauty of the organ that had given her life – thick, veiny, and pulsating with raw power.

Before she could second guess herself, Sarah leaned in and swallowed the length of him whole, her lips stretching wide around his girth. Moaning appreciatively, Mark threaded his fingers through her silken locks, guiding her movements as she bobbed enthusiastically on his shaft.

Turning to Emily, Sarah issued a command, her voice barely audible over the symphony of their heavy breathing. "Join me," she urged, releasing Mark's cock from her mouth with a soft pop.

Swallowing hard against the sudden dryness in her throat, Emily hesitated for a brief moment before obeying. Kneeling beside Sarah, she tentatively reached out and placed her hand next to hers, mimicking the movement as they stroked him together. Emboldened by her sister's encouragement, Emily leaned in and planted a soft kiss on the tip of his cock, tasting the saltiness of his pre-cum on her tongue.

Mark shuddered at the dual assault, torn between wanting to prolong this euphoric agony and surrendering to the inevitable conclusion. Desperate to maintain control, he gritted his teeth and uttered a warning. "If you girls keep this up, I won't last much longer."

Mark managed to gasp out between ragged breaths, struggling to maintain control as the dual onslaught of Sarah and Emily's eager mouths threatened to send him spiralling over the edge.

However, Sarah seemed determined to claim victory first, her body trembling with anticipation as she straddled Mark once more. She positioned herself above his still-erect cock, gripping it firmly before guiding it towards her slick entrance. With a triumphant moan, she sank down onto him, impaling herself fully on his length.

The sensation of being surrounded by warm, wet flesh proved too much for Sarah to bear. Her breath hitched as she felt her orgasm building rapidly, fuelled by the knowledge that she was committing an illicit act with her own father figure. Unable to contain herself any longer, Sarah threw her head back and cried out, her pussy contracting violently around Mark's cock as she came hard.

Streams of milky fluid flowed from between her legs, coating Mark's shaft and pooling around his balls. Still shuddering with the aftershocks of her powerful release, Sarah slowly lifted herself off him, allowing his slickened member to slip from her grasp.

Sarah glanced anxiously towards the doorway, fear creeping into her features. "Quick, Em," she urged, her voice barely above a whisper. "Get on his cock before Mom comes. And just let him cum inside you, okay? We don't have time to clean up; she's almost here."

Emily hesitated for a brief moment, torn between obeying her sister's command and voicing her concerns. Ultimately, though, the allure of experiencing the illicit thrill of being filled by her stepfather's seed proved too great to resist. With a flicker of excitement in her eyes, she swung one leg over Mark's prone form, aligning herself perfectly above his still-erect cock.

Guided by Sarah's steady hand, Emily lowered herself gradually onto him, gasping as she felt his thickness stretch her walls. Once fully seated, she paused, adjusting to the foreign invasion before beginning to ride him with increasing enthusiasm.

Outside the room, footsteps echoed ominously through the hall, signalling Linda's impending arrival. Panic surged within the trio, prompting them to redouble their efforts. Faster and harder, Emily bucked her hips, grinding herself against Mark as Sarah encouraged her onwards.

Time seemed to slow as they hurtled towards their climactic finale, every movement charged with electric tension. Just as Linda's key clicked in the lock, Mark's body tensed, signalling his imminent release. Desperate to complete their task before discovery, Sarah grasped Emily's hips, holding her still as Mark pumped furiously into her welcoming depths.

With a final thrust, Mark emptied himself inside Emily, flooding her fertile womb with his potent essence.

With a jolt of panic, Sarah and Emily hastily disengaged themselves from Mark, their movements frantic as they searched for scattered articles of clothing.

Mark, too, scrambled to cover himself, hastily zipping his trousers and tugging his shirt into place. Time seemed to slow as they worked tirelessly to restore order, every second stretching into eternity as they waited for the other shoe to drop.

Finally, just as they completed their hasty transformations, Linda strode into the room, taken aback by the chaotic scene before her. The two sisters were laughing

Amidst the laughter and jesting, the four settled back into their usual dynamics, strengthened by the shared experience. While the initial misunderstanding had sparked uncertainty, the resulting camaraderie served to reinforce their connections, proving that even in unlikely circumstances, happiness and unity could prevail.

As Linda entered the living room, she found her family gathered around the television, engaged in a lively discussion about the show currently playing. Mark sat comfortably on the couch, with Sarah nestled against him while Emily occupied the armchair nearby. Everyone appeared relaxed and content, as if nothing out of the ordinary had occurred.

Surprised by the mundane scene, Linda questioned, "Everything alright here? I thought I heard voices raised earlier."

Mark, seeming genuinely puzzled, responded, "No, everything's fine. We were just catching up on our favourite series. Want to join us?"

Linda hesitated for a split second before deciding to sit down. As she settled in, she casually glanced at Emily, who sat cross-legged in her chair. Her eyes narrowed as she noticed something odd about Emily's shorts.

"Emily, dear," Linda began, pointing at her daughter's crotch area, "there seems to be a huge stain right in the middle of your shorts. And...is that something dripping?"

Embarrassment coloured Emily's cheeks as she quickly stood up, excusing herself to freshen up. Meanwhile, Sarah exchanged a knowing look with Mark, amusement dancing in her eyes. Little did Linda suspect that the mysterious substance was actually Mark's sperm, leaking from Emily's recently deflowered pussy.