Backseat Sister
by Guzzler21
Copyright© 2026 by Guzzler21
Emma was Freddy’s sister. They had always been at each other’s throats growing up.
If one were to say it was a love/hate relationship, it was more of the hate than the love.
Freddy was the older brother, and Emma had always used this fact to get lenient treatment those times when Freddy reciprocated.
So, over the years, he learned not to fight back. Just try to ignore her and count to ten.
But now that they were both young adults (18 and 20), Emma’s teasing had shifted to more of an annoying flirting.
She was much smaller than him, of course. But in recent years, she had begun to grow, in all of the womanly places. She had a good-sized rack, a very prominent and firm ass, and the legs to go with it.
She often wore her blonde hair in a ponytail or braids, which made her look much younger than 18.
She still behaved like a brat, though. But instead of stealing his things or pinching him, as she had always done before, she was now starting to flirt with him. Anything to get Freddy’s attention.
She was always wearing skimpy clothes. Very tight shorts, too-short skirts, or loose crop tops that would reveal her boobs to him whenever she leaned over or spun around in front of him.
In a way, it was harder for Freddy to ignore her now than during their growing up.
A couple of months ago, she’d been jumping around on his lap while he was trying to watch TV, thumping her ass over his crotch with all kinds of excuses. Freddy’s manhood had reacted after a while, and Emma noticed.
After that, she was relentless. If he was passing by her in the hallway, she’d ‘accidentally’ bump into him - always swiping her hand or her butt over his crotch. Every time she’d showered, she’d come into his room looking for something and either dropping her towel or bending over in front of him so he got an eyeful of her ass and pussy.
And it was a nice pussy! She was always clean-shaven, the outer lips were faintly pink in hue, and her slit always looked moist.
Many a night Freddy had images of his sister’s boobs, ass, or pussy on his retina as he was trying to sleep.
Although he had made an oath to himself to never picture his sister when he jerked off!
It had only happened once! Well ... or maybe twice...
OK! It had happened a lot. He’d tried really hard for a long time to think of anyone else than her when masturbating. But it happened so often, several times daily, that she somehow flashed herself, flirted with him, brushed her breasts against him, or in other ways played lewd tricks on him, that she had now booked a room in his brain’s spank bank!
Freddy excused himself with the fact that it was all just fantasy and imagination. No harm done. No one can know what’s in his mind anyway.
Just a few months ago, only a week after the sofa incident, Emma had started sending him selfies of herself. They were always with some kind of erotic tone. Either she was sucking on a popsicle or wearing some sexy lingerie and asking him what guys might think looks good on her.
At first, he rolled his eyes and just deleted them.
But some of the ‘better’ ones he had put in a special folder on his phone.
He felt embarrassed about it, but ... it couldn’t be helped. Annoying as she was, she was sexy as hell!
Also, Freddy was in the position that he hadn’t been with that many girls. Or ... any girls really. He’d made out at a party a couple of times. But he was too shy around girls. So the one and only girl he’d even seen in the nude was Emma, his skimpy little sister who was always nagging him for attention.
Once in a while, it did happen that she was not all hyper and groping at him or showing off her assets to him ‘accidentally’. Those times were very nice.
They’d be watching a movie or something, Emma would lean against Freddy’s shoulder and he’d stroke her hair or something. Those times were nice. It was like having a girlfriend to just cuddle with.
Other times her advances were more obvious. One time recently she had been in his room, acting annoying as always.
Emma had started fiddling with one of Freddy’s model craft airplanes he kept on a shelf.
It was an old one that he had made years ago, but still, it had a place in his heart.
“Why do you keep this old shit around?” she had asked, “Oops!”
Freddy turned around from his desk and saw his perky little sister there. His model airplane in one hand, the wing of it in the other!
He saw red and flew out of his chair.
As he tried to take the model from her, she sidestepped and he instead banged his head against the bookshelf where she took it from.
Emma seemed to notice that she might have gone too far this time and had a worried look on her face as she tried to move towards the door for an escape!
Freddy’s rage gave him unnatural speed and he was in front of the door before Emma even had the chance to move her feet.
She gave off a nervous giggle as her eyes darted around the room, looking for another escape.
Like two gunslingers before the draw, they both stood dead still for a moment. Emma acted first and threw herself over his bed to get to the other side of the room. But Freddy was lightning fast and grabbed her by the ankle before she could clear the bed.
He pulled her toward himself and grabbed her other ankle also.
Emma giggled with fearful anxiety, “I’m sorry! I’m sorry!”
She felt that she had gone too far this time in irritating her brother and was a little afraid of the repercussions now.
Freddy tugged at his sister’s flailing legs and climbed up on the bed above her. In an attempt not to get kneed by her wildly thrashing legs, he pushed himself over her and used his hip to pry them open around him. Being so much taller than his sister, he had no problem grabbing her wrists and pinning her arms above her head.
Emma was still bucking her body, trying to escape from under him. Freddy laid all of his weight on her to secure her under him.
Emma’s short, flimsy skirt had been coiled up between them, and he could feel her stiff nipples pressing into his upper belly. She was huffing and hissing beneath him, in futile attempts to break free from his grip. Freddy felt her smooth thighs pushing and sliding over his hips and midsection. He was still angry, but was feeling a curious calmness flow over him.
He had his buxom little sister in a strong vice under him. Her chest and breasts were pushing against him, and as he put some weight on his hips, he could feel her legs being forced apart around him. Finally, he had his pelvis pressed heavily against her nethers.
Emma was still trying to wiggle around, but was firmly held in place by his body.
He could feel her pussy mound through the thin fabric of her exposed panties pressing against his bulging pants.
Emma stopped and became still. Their eyes met, and for a moment, nothing happened.
Then Freddy could feel a familiar tingle down below. Blood was rushing towards his member. The realization of where it was placed alerted his primal instincts, and his body got to work.
In Emma’s big blue eyes, he could see that she also was perceiving what was happening down there.
It took a second for Freddy to objectively grasp what was happening. The small Neanderthal part of his brain wanted to stay where he was. Pressing this hot and horny little creature under him, having their privates so tightly connected. He felt heated.
But sanity won the day. Freddy lifted himself off of his sister and let go of her wrists.
“Get out of my room,” he said in a demanding tone and pointed towards the door.
It was hard for him to control his eyes now. Emma lay there on his bed. Splayed out. Her thin t-shirt was crumpled up, revealing her naked belly, and her skirt was flipped up, exposing her white panties. Her legs were still widely parted.
She looked at him with big eyes and flushed cheeks.
Emma slowly collected herself, straightened out her clothes, and slipped out of his room.
Freddy closed the door behind her and took a deep breath.
He was happy that he had controlled himself. But the sense of being so close to losing control was there. He could’ve just rubbed himself up against his pinned sister. There would be nothing she could do to resist him having his way with her just now. Maybe she’d even let him do whatever he wanted to her. It was a bizarre and scary thought.
Freddy was fully hard now. Luckily, he stopped when he did.
The image of his cute, sexy sister laid out on his bed went straight into his memory’s spank bank.
They both lived at home still, and as always, in the fall, it was time for family vacation.
And this year was no different. Well, the difference was that Dad’s car was at the shop, and the one he got to borrow as a replacement was very much smaller!
Mom had been very worried about whether all their luggage would fit and told the family that everyone had to pack very lightly this year.
The cabin they always stayed at was nicely located by a lake, in the forest. It was a long drive there, but it had all the luxuries of a normal home once they got there.
On the day of the trip to the cabin, their mother had not heeded her own advice about light packing. She’d brought even more stuff than usual. Their parents argued a bit, but Mom’s excuse was that now that everyone had packed so little, she’d packed even more, in case anyone had forgotten something!
This resulted in there being only one seat left in the backseat. Emma and Freddy would have to share! Freddy rolled his eyes as Emma reveled in getting to sit in her brother’s lap for hours on end!
She was today wearing a pair of those super tight training pants that leave nothing to the imagination. The pattern was some kind of snakeskin, with futuristic lettering here and there. It was very obvious to Freddy that she wasn’t wearing anything underneath.
As Freddy was walking out the door, he had to pass Emma who was in the way.
Emma, of course, pushed her ass out and collided dead centre on Freddy’s semi-hard dick.
Freddy could feel her soft pussy lips part over his dick that he had hidden in his Bermuda shorts. Emma felt it too and teasingly rubbed her ass up and down on him before he managed to push her off and break free!
He heard Emma giggling as he made his way to the car with his last bag.
He crammed it onto the seat in the back and there was now a pile of bags and luggage filling up the other seat next to him. Bags and suitcases were piled up to the ceiling of the car.
He dreaded what was next.
“Are we all ready to go?” he heard his dad shout from inside the house.
He saw Emma skipping towards the car. Her braless tits bouncing under her tiny t-shirt.
“I’m just gonna stretch out before the long trip”, she said while looking Freddy in the eyes.
Emma stopped by the open car door. It was the kind of small car that only had two front doors. So to get in, one had to fold the front seat forward to get into the backseat.
Freddy was already seated, his lap clear for Emma to sit on.
Emma turned her back to him and with very exaggerated moves started stretching and bending forward. Of course, to display her butt to her brother and egg him on teasingly!
Freddy tried to look away ... but his eyes, as they often did, betrayed him and he stole some glances. It was obvious she didn’t have any panties under those tights.
It was a sight to see, as always. Emma did really have a nice ass. It was pretty big for her petite figure, but well-rounded and firm at the same time. Those tights didn’t do anything to hide that fact.
Dad came out of the house, “Alright, Emma. Get in the car. And no fighting there in the backseat”, he said jokingly.
It had been a long time since they had actually fought like siblings in the backseat. But it was the typical dad thing to say, of course.
Freddy rolled his eyes and scooted back on his seat to make as much room as possible in the cramped space.
Emma stepped in and sat herself heavily on his lap.
She started twerking and rubbing her bum around over him.
“Sit still, Emma”, Freddy said.
“I’m just trying to get comfortable”, she complained, but with that teasing giggle she always had.
But all her ass rubbing on his lap had the effect that his shorts were slid down, and since he wasn’t immune to Emma’s voluptuous curves, he was also feeling a growing erection. The head of his dick was now peaking out over the hem of his shorts!
Freddy tried to slide himself down, hoping that this would pull his pants back up to cover his cock, but Emma pushed her behind backward at the same time.
They both froze in place when it became clear that the tip of Freddy’s dick was now pressed up against Emma’s tight labial lips!
Only one thin layer of fabric separating them from each other.
He could feel Emma clenching her muscles, softly pressing and releasing against the head of his half-swollen glans!
She was probably loving it, Freddy thought. To teach her a lesson, he grabbed a pinch of her tights in each hand, pulling the fabric of her tights outward with the aim to let it go and smack her outer thighs as the fabric snapped back!
But instead, he heard a rip and felt the protective fabric between them disappear in an instant!
Her body weight pressed her downward, and his cock found that its way upward was no longer blocked! His smooth glans slipped in between her wet folds!
He heard Emma gasp and felt the heat of her slippery skin against his own sensitive tip!
There was now a new blockade pressing against his tip! Emma’s entrance had clenched shut, as to protect itself against the sudden intruder pressing against it.
Time stood still! This was actually what Emma had always been wanting and hoping for when she teased her older brother. But now that she was there, it was a bit scary!
Her crevice was already wet. She was always wet. But the only thing now hindering Freddy’s cock from slipping into her was her entrance muscles. She could feel it almost give way; he was pressing hard against it.
That’s when their dad poked his head in!
“Here!” he said and shoved 2 heavy carry-on cases onto her lap! It was the kind with wheels that you can bring along on an airplane. But they were loaded to the brim!
The weight was too much for her little entrance to bear!
With the heavy luggage placed in her lap, Emma sunk down on her brother’s glans, just an inch. But it was enough to press his head in through her resisting hole!
Emma let out a squeal!
“Come on, Emma. It’s not THAT heavy”, their dad mused, “Put out your arms”, he told her.
Emma’s brain was now very preoccupied with what had just pressed into her most secret place, so she didn’t think to question or ponder her father’s directions.
The carry-on luggage reached up from her thighs to her armpits. She laid her arms out flat over them, and Dad dumped a large and heavy hockey trunk over them. It filled the rest of the space in front of her face and the driver’s seat! Her arms were pinned!
Freddy felt his sister’s hole press tightly around his swelling helmet in there! The feeling was excruciating! He had even forgotten to breathe for a while! She was so immensely hot inside!
It was almost a burning feeling around the tip of his now twitching cock!
“Pull it out!” Emma hissed through gritted teeth at him.
“I’m stuck!” was all he could answer as he felt his dick now quickly swelling in size and girth, pressing more of itself into his trapped sister’s wet crevice!
Emma whimpered, partly in fear and partly in pleasure. Although this was not something she was ready for, the feeling was intense and very pleasing!
Emma had used toys on herself several times, but never had sex for real. And the toys she was used to were of the smaller versions.
Now she had a real-life cock pressing into her. It felt so big! She could feel her muscles contracting around it. She could feel it growing in size ... and length!
Emma felt her whole body get goosebumps.
Freddy was still in shock from the situation that had unfolded. His dick was now on autopilot, growing and swelling, trying to get as deep into the warm, wet place it had discovered.
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