On My Younger Brother's Lap

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Disclaimer:

This story contains mature themes, including violence, taboo subjects, and psychological tension. The actions of the characters are fictional and are not intended to endorse or condone harmful behavior. All characters are depicted as being over the age of 18. Reader discretion is strongly advised.

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The road buzzed beneath the tires, the sky outside bruising into night. Warm air poured in through the cracked windows, thick with the salt of the sea and the refreshing fruit trace of weed.

Isa had a plastic cup balanced in one hand, cheap rum mixed with flat Coke, still cold against her fingers. Her bikini was clinging in all the wrong places. Still damp, still tight and she could feel the fine layer of salt drying on her skin.

They were packed tight in the car, legs tangled, bare shoulders sticking where skin met skin. When the cops arrived, everyone threw their towels and backpacks inside. The blunt hadn't been fully smoked before they were on the road again.

Laughter had faded to slurred murmurs and open-mouthed sleep. The driver, Sam, had both hands on the wheel, eyes fixed ahead, brows drawn. The front passenger was snoring. Everyone else was either dozing or pretending to.

Which meant no one really noticed her. No one but Josh.

He was quiet beneath her, thighs wide, one hand braced against the door and the other casually on her hip. It was the only seat left when they piled in. As siblings, it's not something they had never done before... but usually they wore more than swimwear and they often were significantly drier.

She was used to having him close. Growing up, he was her little shadow, two years behind in school and still growing into his body.

But grown, he had. He wasn't built like a boy anymore. He turned eighteen at the beginning of the year. His chest was broad, pecs firm under the thin cotton of his tank. His arms were tan, lean, dusted with dark hair and warm against her sides. His legs under hers were solid and subtly muscular in the way of someone who was starting working out more consistently.

The softness was gone. His body wasn't familiar anymore. He wasn't the little annoying brother anymore. It felt like something she shouldn't notice, but couldn't help feeling.

And then she shifted.

Just a little.

A tilt of her hips, angled to take the pressure off him. She thought maybe she was helping. If he was awake, he'd be mortified.

She could feel how hard he was, and they hadn't even looked at each other since she sat down. So she tried to spare him, tried to ease the weight, to make it less obvious.

But her new position only made it worse.

Now his arousal was pressing exactly where it shouldn't.

It was unmistakable.

His bulge cradled right against the tender spot beneath her. Her breath caught, her thighs reflexively squeezing just a little. Her heart beat harder.

She turned her head, slow, careful. Josh's eyes were shut, but too tight. His jaw was rigid. His nostrils flared just slightly as he breathed through them, too controlled.

Not asleep. Pretending.

And underneath her, something pulsed. It was thick. She could feel him twitch. He was getting even harder. She thought his shorts would explode, and she imagined the girthy cock beneath.

Something shifted inside her too.

Heat. Perhaps more like electricity. A low, vibration that started in her stomach and uncoiled downward, leaving her tense and restless. Her suit rubbed against her clit with every movement, fabric riding higher. Her thong was burying deeper into her slit, all the way to her ass. Her thighs were slippery again, the whole situation was making her nervous and sweaty.

Could she pretend she didn't notice?

Josh was just eighteen. Isa was two whole years older. He had that wide-eyed quiet about him, the kind that said he'd probably never had a girlfriend. Not a real one. She doubted anyone had ever sat on his lap in a wet bikini after too much rum and pressed herself into his cock without saying a word.

He was her little brother and she had to stop.

But her body wasn't listening. She was filled with something shameful, but why hadn't Josh stop it.

What if someone realised what was going on?

No one could know.

Which somehow made it worse.

And somehow... much better.

The rum was catching up with her. That slow, syrupy warmth was seeping into her limbs, spreading like honey just under her skin. Her head felt floaty, loose in the best kind of way, like her thoughts had come untethered, drifting just behind her in the wind that blew through the cracked window.

Her body was eager now. Not just the vibration from the road or the soft bass from the front speakers. It was inside her. From the press of Josh's body under hers. From the heat blooming between her legs. From the drink blurring the edges of her restraint.

Her skin felt tight, flushed. Her bikini top clung damply to her tits, the triangles of fabric stretched just slightly from the way she'd shifted. Her nipples were hard. She could feel them grazing the lining, sensitive to every movement, every breath. The soft under-curve of her breasts was slick with sweat and salt, and the cool air from the window made the contrast sharp, teasing.

Her thighs were bare and sticky against his. Her legs, toned from too many summers of volleyball and hiking trails with friends, were parted just enough to straddle his lap. She could feel every contour of his hard dick beneath her.

She wasn't doing anything. She hadn't even moved.

Not really.

But her suit was soaked through now, and not from the ocean. The strip of fabric between her legs was pulled tight, pressing into her, gliding slightly as the car jostled over a rough patch of road.

It was maddening.

Arousal was slipping into her bloodstream, mixing with the alcohol. Her buzz wasn't just from the drink. It was from the friction. She needed more.

She tilted her head back slightly, eyes half-lidded, pretending to look out the window.

But all she could feel was him.

All she could think about was what he must be thinking.

Her little brother. Sitting perfectly still, pretending to sleep, while she shifted over his cock in nothing but a wet bikini.

Usually, when Isa was getting ready for parties, he would tell her to cover up. That men would stare at her. So she would tease him saying that it was okay for him to feel so protective of his beautiful sister. That would make him shy, letting her finish her makeup.

She could never have imagined for him to be this turned on. Was it because of her? Or maybe he got hard at the wrong time.

The car hit another bump.

The pressure slid again. Deeper now, angled perfectly and her breath stopped. Her hips twitched before she could stop them, just a reflex.

Josh tensed under her.

She froze.

She should stop. She should laugh. She should make a joke, pull away, say something about how cramped it was in the backseat.

But instead, she exhaled through her nose, slow, steady, and let her hips settle back down... right there. His bulge had moved beneath her. Not rubbing against her lips. Poking into her pussy. Had they been naked, he would have been inside her.

Isa let her body relax, sinking into him inch by inch like it wasn't on purpose.

Her back pressed softly to his chest, her bare shoulder resting beneath his jaw. She could feel the rise and fall of his breathing. The buzz was thick inside her now, syrup-slow and golden, turning each breath into something full of weight and heat. It seemed like the world was turning at high speeds.

Her thighs squeezed together, as if to trap the sensation between them. It didn't help. It only made it sharper. It was stimulating her, a fuzzy feeling teasing her insides.

Her fingers drifted down, quiet, unthinking, just needing something to touch. She let them curl gently over his thighs. They were warm beneath her palms, his skin slightly rough from salt and sand, twitching faintly beneath her fingertips. Solid. Strong. The feel of him made her stomach twist.

Her breaths grew uneven.

The rhythm was betraying her. Little stutters in her chest, a shiver in the way she exhaled. She tried to hide it by going still. She bit the inside of her cheek. Focused on the window, the sky, the music...

But then, without warning, his hands came down. Hesitantly.

And settled right on top of hers.

Isa stiffened just for a second.

Josh didn't grip. Didn't squeeze. Just laid his hands there, his palms large and warm and trembling the smallest bit.

She could feel the uncertainty in them. The restraint. But also the awareness.

He knew where her hands were.

He knew what she was doing.

And now he was part of it.

Her heart skipped.

She swallowed hard, tried to keep breathing evenly, but her chest was rising too fast. Her nipples were aching, her thighs slick, her suit stuck tight to her now, too tight. She could feel herself getting wetter, and the faint throb of need pulsing like a second heartbeat between her legs.

She didn't dare look at him.

If she did, she might not stop.

Instead, she let her fingers shift slightly beneath his. Just enough to press her palms a little firmer to his thighs. To let him know she was still there. Feeling everything. Every inch and every throb.

The road stretched on in silence.

No one else stirred.

The music played low.

Her back and his chest were sticking together, skin to skin, sweat to sweat. The humid warmth of the car wrapped around them. Every bump in the road rocked her against him just a little more, as if the space between them no longer wanted to exist.

Isa shifted again, slower this time, letting her weight settle more fully. The tip of his cock pressed right where it wasn't supposed to, and her pulse stuttered again in her throat. She turned her head, her cheek brushing against the soft fabric of his tank. Her lips were close now to the side of his neck. He smelled like sunscreen and salt and something else. Something warm and boyish and newly unfamiliar.

She opened her mouth.

And for a moment, she didn't speak.

Instead, she let her breath slide out. Right against the shell of his ear. A whisper of heat. A brush of sensation she pretended not to notice.

She felt him flinch. The small hairs on his neck rising. Goosebumps on his skin.

She let it hang, then leaned in that last inch, her voice barely there.

"I'm not too heavy?" she whispered.

His fingers twitched against the backs of her hands still resting on his thighs, still caught under his own. She felt his stomach tighten, a shallow inhale like he wasn't sure whether to laugh or confess something.

Then, finally, so quiet she almost missed it:

"No."

A beat passed. His voice came again, rougher now.

"You feel... good."

Isa didn't move.

She couldn't.

Every part of her was strung tight now, her thighs trembling, his heart beating loudly in her ears. The buzz of alcohol and arousal had fused into something molten, spreading through her belly, her limbs, the wet heat building between her legs.

Josh hadn't shifted beneath her. Not much. But he was very hard, and the thin barrier of her bikini was soaked, clinging to her pussy. You couldn't wrap rope around her tighter than the cloth inside her pussy right now. She could feel him entering.

She hadn't realized how little fabric was between them. How easily it had moved. How wet she was.

And now he was pushing. Breaching ever so slightly.

She sucked in a breath.

His cock was slipping past her folds, her bikini bottom helpless to stop it. The fabric had shifted just enough, must have been accidentally pulled to the side leaving no resistance.

It was uncomfortable, and painful, but the more seconds went by, the wetter she got.

He had never felt it this way before, let alone seen it. Her baby brother was packing a thick tool between his legs.

Isa's hips twitched. She felt herself stretch around him, the first inch sliding in, warm and uninvited, but somehow exactly what her body had been begging for.

Her fingers dug into his thighs.

She didn't mean to.

She was breathing too fast now, trying to hold back the sound, but the feeling was raw and aching.

And still, Josh said nothing.

But she could feel him trembling. His breath hitched against her shoulder. His hands, still on hers, clutched now, holding her.

As if he was just as terrified to move as she was.

What are we doing?

That thought flared up way too late. And she was too weak now to stop.

And she hadn't told him to stop.

She hadn't told herself either.

Isa didn't know how she was still breathing.

Her body had gone soft and tight at once. She melted against him but clenching around the pressure that pushed into her.

But his swim shorts were still on.

That single, thin layer of damp nylon. A barrier that meant nothing now, clinging wetly to his skin, riding low on his hips, stretched tight where he was hardest. He'd soaked through. She'd soaked him through. That scrap of fabric was all that kept them from something they'd never come back from.

It was obscene how easily he was pressing through it. How the head of his dick had found her anyway, nudging past the edge of her bikini, meeting her body with shocking precision. Her folds were parted around him now, cradling him, teasing him, sucking him in.

But the rest of him was still caught behind that useless fabric. Still wrapped in the thinnest veil of denial.

A condom made of swim shorts.

A breath away from full penetration.

A whisper away from what they couldn't undo.

And Isa felt it. Felt it in her core. That impossible pressure, right against where she ached, where she throbbed.

Close enough to feel the heat of him.

Close enough to know the shape of him.

Would they do it? Had they been alone. Just her and her little brother.

She would have torn his swimsuit off of him body, revealing his aching cock, ready to fuck her.

Her breath hitched again. Her thighs squeezed. Her hips rocked.

Josh moaned.

It was tiny. Barely audible.

But it was the first sound he'd made since her question.

His hands weren't just holding her now, but pulling her into him. His body pushed up against hers. Trying to go as deep as he could. His cock was trapped in his shorts, but he could almost taste his sister's pussy.

Isa silenced her own gasp. A warmth began to pool between her legs. Right inside her. He was blowing his load. His hot cum shot out, oozing through his shorts. She could feel it sticking to her.

Josh's breath had steadied against her shoulder, his hands releasing their rough grip.

They sat in silence, afraid to move. When they finally returned, they pretended they'd just woken from a long nap. Neither spoke. They waited until the car emptied.

When Isa finally stood, sticky cum dripped out of her, pooling on top of his shorts. They wiped themselves off with towels in silence.

They didn't need words.

A door had opened and neither of them was going to close it.