Skip to content You know those viral gym fails where dudes show up in flip-flops, or the benches collapse mid-rep, and everyone in the comments just roasts them to hell? Today, I was that guy. Only, it wasn’t a bench that failed me, it was the goddamn gym itself. Closed for emergency maintenance, which is code for the air-conditioning busted and some horny teen jerked off in the sauna again. I slouched home, sweats sticking to my legs and the beginnings of a headache thudding in my forehead. At least I had a free afternoon.
But the closer I got to my house, the weirder it felt. From inside, the bassline of Dua Lipa was rattling our living room window. Which meant my older sister was home. She never played music that loud unless she was a) drunk, b) cleaning, or c) in the middle of a workout and high on endorphins. Judging from the way the house actually shook every three seconds, I was betting option c.
I nudged the door open with my foot and tripped on a yoga mat splayed like a booby trap in the front hallway. The inside of the house had this sharp, sweet smell of tropical body spray mixed with sweat. The living room had been converted into a makeshift gym: dumbbells lined up along the TV stand, resistance bands dangling from the couch, a huge water bottle perched on the ottoman. Center stage was my sister, Ava, older than me by three years, 23, hotter than most Instagram influencers, and currently wearing a pair of shorts so small they looked like the elastic could snap if she breathed too hard.
She had her back to me, balancing a barbell across her shoulders. The shorts hugged her ass, a perfect upside-down heart, riding up so much her tanlines were visible. Her tank top was a cropped, cut-off thing that clung to her ribs, and with every squat, I could see the curve of her waist and a few inches of bare, glistening skin above the waistband.
She was mid-set, in the zone, earbuds jammed in, face scrunched in effort. The bass of the music pulsed with her reps. I stood there for a second, brain buffering, unable to decide whether I should sneak past her or just cough and announce myself. Instead, I just kind of hovered, half-hidden behind the fridge, and tried not to look like a pervert.
She finished the set, racked the bar, and immediately bent over at the waist to stretch, hands gripping her ankles. That made her ass stick out even more, fabric of her shorts pulled so tight that I could basically read the brand name of her thong beneath. She stayed like that for a good fifteen seconds, then straightened, popped her earbuds, and turned to face me.
“Hi there,” she said, wiping her forehead with the back of her hand. “Didn’t hear you come in.”
“Yeah, well, you almost blew my eardrums out,” I shot back, trying to sound chill, but my voice came out kind of weak and weird. I could feel my cheeks heating up already. Goddammit.
She grinned, teeth white as hell, and flopped onto the couch, legs spread wide and elbows on knees. “Gym’s closed … have to workout here instead,” she said.
I shrugged. “I know, maintenance. Probably for the rest of the week.” I deliberately looked at the TV, not her, but she didn’t care. If anything, she noticed me trying not to look and leaned forward even more, resting her chin on her fists so her boobs smushed together and almost spilled out the sides of her top.
“Bummer,” she said. “You wanna work in with me? I’m just doing glutes today.”
“Yeah, I think I’ll pass,” I said. “I’m not about to get shown up by my own sister. Besides, your shorts are giving me an existential crisis.”
She snorted. “Please. You wish your legs looked this good in spandex. Besides, you can’t even handle one of my circuits.” Her voice had that teasing, bratty edge to it that she’d perfected since middle school. I hated it, and kind of loved it.
She stood up, smacked her thighs, and started doing walking lunges across the living room, making a point to really exaggerate the step and drop her ass low. Each time, her muscles flexed and the shorts bunched higher, until I could see the lower curves of both cheeks. She glanced back at me and caught me staring. She grinned, waggled her eyebrows, and said, “Told you, bro. Glute day. Wanna spot me?”
If she noticed the tent in my sweats, she didn’t comment. Instead, she lined up with the coffee table, dropped into a plank, and started doing mountain climbers. Her ponytail whipped side to side, sweat beads flicking onto the carpet. I couldn’t look away. Her back muscles stood out like cords, her legs moved with the control of a gymnast. I got hard watching her, my own sister, and it made my brain do flip-flops. If I didn’t get out of there, she’d definitely notice.
But she looked up, hair stuck to her face, and panted, “Hand me my water?”
I snagged the giant pink bottle from the ottoman and tossed it over. She caught it one-handed, twisted the cap, and chugged half of it without blinking. Water dribbled down her chin and onto her top, leaving two see-through patches around her nipples. She looked right at me, saw my eyes widen, and didn’t even try to cover up. She just wiped her mouth and set the bottle down.
“Sorry,” she said, not sounding sorry at all. “It’s like a hundred degrees in here.”
“Maybe you should wear more clothes,” I muttered, desperate to seem annoyed and not horny.
She laughed, walked right up, and poked me in the abs with her finger. “Maybe you should man up and join me,” she said. “Or are you afraid you’ll lose to a girl?”
Before I could answer, she walked past, so close her hip brushed mine. She loaded up a dumbbell and started doing hip thrusts on the floor, feet braced against the edge of the sofa. Every time she pumped her hips up, the shorts slipped, and her abs clenched, and the whole thing looked exactly like she was grinding on an invisible boyfriend. I think she knew it, too, because she kept glancing at me out of the corner of her eye.
“Okay, are you doing this on purpose?” I finally said, voice way more shaky than I wanted.
She didn’t pause. “Doing what?”
“Bending over and… and…” I waved my hand at her ass. “That.”
She smirked, set down the weight, and rolled onto her side, head propped up by her arm. “You mean working out?” she said, acting innocent but clearly loving every second of my discomfort.
“Never mind,” I mumbled. I should have just bailed, but my feet wouldn’t move, and I did something dumber, I sat down.
Ava flipped onto her hands and knees, arched her back like a cat, and held it for a beat. “You know, if you want a real show, you should stick around for yoga.”
I snorted. “Yeah, I’ll pass.”
She pushed herself upright, hands on hips, and locked eyes with me. “Bet you can’t even touch your toes,” she said, then turned her back, spread her legs, and folded forward in a perfect standing split, palms flat on the floor. The hem of her shorts rolled up even more, and I swear I could see the smooth, dark outline of her pussy. She stayed in the pose, ass high in the air, and wiggled it like she was waving at me.
“Holy shit,” I muttered, and looked away, face on fire.
“Hey, Ry?” she called, still upside down. “You ever heard of ‘downward dog’?”
I grunted, trying to focus on literally anything but her.
She flowed into a full yoga sequence, ending in the classic downward dog pose. Her back was a long, sexy line, ass cocked high, legs spread just wide enough to make me sweat. She held the pose way longer than any normal person would, and every so often she’d peek between her legs to see if I was watching.
“Are you seriously doing this?” I said, trying to laugh it off.
She didn’t move. “What, stretching? You’re such a perv, bro.”
“You’re doing it on purpose,” I accused, but my voice didn’t sound angry. Just… defeated.
She looked back at me over her shoulder, eyes full of mischief. “Maybe a little,” she said, winking. “Don’t act like you’re not into it. I can practically smell you from here.”
My dick throbbed in my sweats, so hard it hurt. I wanted to run, but my body felt glued in place. Instead, I doubled down on sarcasm. “Real mature, Ava. Flaunt your ass, give your own brother a boner, then make fun of him for it.”
She rocked her hips back and forth, then sunk to her elbows, pushing her ass even higher. “That’s kind of the point,” she said, voice low and weirdly sultry. “You’re so easy, Ry. You always have been.”
She held the stretch, breathing deep, then looked back again. “You wanna see what I’ve really been training for?” she said.
“What do you mean?”
She twisted sideways so her ass and tits were both in profile, then grinned. “Doggy style,” she said. “That’s why I do all these glute bridges and squats. Gotta keep my form perfect.”
For a second, I thought my ears were broken. “Did you just say—?”
“Yeah,” she interrupted. “I like fucking from behind. It’s, like, my thing.”
I stared, mouth open, trying to process it. “You’re such a slut.”
“Duh,” she said, shrugging. “That’s the fun part. You gonna help me, or just stand there drooling?”
It was like the last few years of “off-limits” sibling rules just erased themselves from my head. I knew I should say no, but my body wasn’t listening.
She crawled to the middle of the floor, wiggled her ass, and patted the carpet behind her. “Come on. I need a spotter.”
I felt like my brain was floating outside my skull, watching someone else’s life. My hands shook as I dropped my gym bag, rose to my feet and stepped closer. Ava rolled her eyes and reached up to grab my waistband, tugging me forward until my bulge was level with her face.
“Damn, Ry,” she said, running her tongue over her teeth. “Didn’t think I’d get you this worked up.”
My heart pounded in my ears. “You’re crazy,” I said, but I was already pulling down my sweats. My cock sprang out, angry red and leaking at the tip.
Ava looked up at me, eyes wide and hungry. She wrapped her hand around the base and squeezed, then ran her tongue up the shaft and sucked the head into her mouth. It was the first time anyone had ever done that to me, and I nearly blew right then and there. She bobbed her head slow and deep, moaning as she went, and my knees actually shook.
She pulled off with a pop, wiped her mouth, and got back onto all fours. “Fuck me,” she said, voice flat and demanding. “Doggy. I want to see how strong my glutes really are.”
I knelt behind her, hooked my thumbs in her waistband, and peeled the shorts down. Her ass was flawless, tan and round and dusted with sweat, the crack perfectly shaved. Her pussy was slick and swollen, juice already running down the inside of her thigh.
I lined up, pushed forward, and slid inside her in one slow, shuddering stroke. She gasped, shoved her hips back, and nearly knocked me over. The grip of her pussy was insane, hot and wet and squeezing tighter every time I pulled out and slammed back in.
“How does my ass feel?”
I gripped her firm cheeks with both hands, spreading them wider as I sank deeper. “Perfect,” I groaned, almost in disbelief. “Fuck, you feel so fucking perfect.”
She let out a filthy little laugh, then slowly pressed her chest and face down to the carpet, keeping her knees wide. Her back arched deeply as she raised her ass higher, presenting herself like a bitch in heat. The new angle made her pussy grip me even tighter.
“Like this?” she purred, wiggling her hips so her round ass jiggled against me. “This is how I practice. Tell me how good your big sister’s pussy feels wrapped around your cock.”
The taboo words hit me like a slap. My own sister, the girl I grew up with, was on all fours with her face pressed to the floor and her ass up in the air, begging for my cock. It was so wrong, but it made me throb harder inside her.
“So good,” I growled, pulling back and slamming into her again. The wet slap of skin on skin filled the living room. “You’re so fucking tight, Ava. I can’t believe I’m inside you.”
She moaned loudly, pushing back to meet every thrust. “That’s it, little brother… fuck your sister harder. Use me.”
I lost control and started pounding her deep and rough. Her perfect ass rippled with every brutal thrust, the sound of my hips smacking against her echoing through the house. Her pussy was dripping, creamy juices coating my cock and running down her thighs.
Ava reached back with one hand and spread her ass cheek for me, giving me an even better view of my cock disappearing into her tight, pink hole. “Look at you stretching your sister’s pussy,” she gasped. “Does it feel good knowing you’re balls-deep in family?”
“Fuck yes,” I admitted. “It’s so wrong… but I don’t want to stop.”
“Don’t stop,” she begged, pressing her face harder into the carpet and raising her ass even higher. “I need to train, you know.”
The words destroyed whatever was left of my restraint. I fucked her like an animal: hard, fast, and deep, gripping her hips so tight I knew she’d have bruises. Her moans turned into desperate whimpers as her pussy started clenching around me.
Her whole body shook as her orgasm hit. Her pussy spasmed violently around my cock, milking me with sweet pulses. The feeling was too much. I buried myself as deep as I could go, my hips flush against her perfect ass, and exploded.
Thick ropes of cum blasted straight into my sister’s vagina. I kept thrusting through it, grinding deep, pumping load after load into her clenching pussy. The sensation was overwhelming: hot, wet, and intensely taboo. I was cumming inside my own sister.
Ava moaned loudly as she felt me filling her, pushing her ass back to take every drop. “Yes… give it to me. Fill your sister’s pussy.”
We stayed locked together for a long moment, both panting. My cock twitched inside her as the last spurts drained into her. When I finally pulled out, a thick river of my cum oozed from her freshly fucked hole and dripped down onto the carpet.
Ava stayed in position for a few more seconds, face down, ass up, like she was showing off her work. Then she looked back at me over her shoulder, flushed and glowing, with a satisfied, wicked smile.
“Best workout I’ve had in weeks,” she said breathlessly. “We should do glute day more often, little brother.”
I wiped my forehead, heart still racing, and collapsed onto the carpet. “What the fuck, Ava,” I said. “I can’t believe we just did this.”
“But we did.” She shimmied her hips, still leaking, and smiled. “I’m gonna need to train again tomorrow. You in?”
I couldn’t think straight. I just nodded.
She rolled onto her side, sprawled out like a sunbathing cat, and said, “You bring the water. I’ll bring the ass.”
I wondered if the gym would ever reopen. For once, I hoped it wouldn’t.
Enjoyed this story?
Browse the books → Incest Books
Get 50% off your first order.
Use code: FIRSTREAD
Or if you want to read similar stories → Brother sister incest stories