As non-identical twins, Mark Goldman and his sister Libby had always been close. They played together quite harmoniously, to the delight of their parents. One night they grew even closer...
A teenager babysitter named Sheila was watching the kindergarten-aged twins while their parents went to see a concert. Mark and Libby were upstairs watching a movie when Sheila quietly let her boyfriend Steve in the backdoor. Sheila and Steve were both seventeen -- they were typical horny teenagers who'd been fucking non-stop for weeks now. Sheila was almost immediately naked and bouncing up and down on Steve's 7" cock as he sat on the Goldmans' living room couch. The teen babysitter's B cup tits were bouncing around in Steve's face -- he couldn't help but groan as he sucked her tiny, hard little nipples while she rode his cock.
Sheila groaned too, then she gasped when she heard a creaking noise and looked up to see the twins watching them from the stairs! Steve turned around and grunted with surprise. Sheila stayed still atop his raging prick, his cockhead buried in her womb. The twins were wide-eyed, ogling Sheila's pert tits and lithe, tan, nude body. They couldn't see her neatly trimmed patch of pubic hair or Steve's cock, but the twins were certainly intrigued by the groaning and movement and Sheila's naked body. Neither of them knew what Sheila was doing, but it looked fun!
"Oh, uh, hi kids, this is my uh, my brother Steve. I haven't seen him in awhile, so I was just giving him a really big hug," stammered Sheila, still sitting on Steve's cock. His prick didn't show any sign of deflating. "Go ahead and go back up to your bedroom, I'll be up to check on you kids soon, okay?"
Sheila continued riding Steve's cock to climax once the children were out of sight, letting Steve sperm up inside her. Libby and Mark went back upstairs to the bedroom they shared, but they didn't resume watching the movie. They laid next to each other in bed, their young minds trying to comprehend what they babysitter and her "brother" had been doing down in the living room. Libby felt a curious tingling between her legs -- her pussy was aroused, though she didn't even know it. It seemed like Sheila really loved her brother. Mark and Libby loved each other a lot, too...
Later that night, after their parents came home and checked on them and then retired to their own bedroom, Mark turned to Libby in the moonlight. They were laying on Mark's bed down on the bottom bunk; often they fell asleep together on the same bed. Libby had on a thin pink nightgown with pink cotton panties. Her nipples were hard in the chill of the night. Neither of them had been able to fall asleep. Mark had been laying there, staring at the shadowy lumps that were his sister's tiny, hard nipples poking through her nightgown in the moonlight. He was thinking about Sheila's breasts, his small cock twinging occasionally. Would his sister's look like that someday? All plump and lovely?
"Psst, Libby..." whispered Mark. "Are you sleeping?" Libby opened her eyes, facing her twin brother.
"No," she whispered back. "Not really."
Mark sat up. "Why don't you try sitting on me, like we saw Sheila doing downstairs?"
Libby's heart skipped a beat. She sat up and faced her brother in the shadowy darkness of their bedroom. Undeniably, she'd been thinking about what she'd seen as she tossed and turned next to Mark. What Sheila and Steve were doing was so strange, so curious, so alluring... Mark got up and silently walked to the bedroom door, taking Libby by the hand and leading her downstairs. They crept to the living room, where Mark sat down on the couch in the same spot Steve was in. He pulled Libby onto his lap. Her heart pounding fast, she let her brother hold her body tightly against him. Her crotch pressed hard into his and she gasped -- it was a surprising feeling, a feeling of pleasure she'd never felt before.
Mark helped Libby bounce up and down on his lap like they'd seen Sheila doing with Steve. Neither really knew what they were doing. Mark grew to increasingly enjoy the feeling of his sister's crotch grinding into his, his little prick getting harder and harder. Libby liked bouncing up and down on Mark, too -- especially as his penis grew harder against her crotch! Mark had never really experienced an erection before. And although Libby didn't know it, she was working herself up to an orgasm. This was indeed a fun hug! But before Libby could experience her first climax, they heard a floorboard creak upstairs and she immediately jumped off his lap and ran to the kitchen.
"Kids?" called their mom, Louisa, from the top of the stairs. "You better not be rummaging around in the fridge! It's after midnight, you know!"
"Sorry mom!" Libby shouted back.
"We're coming back to bed now," Mark shouted. "Good night!"
"Good night, get some sleep, kids. Love you!"
Mark and Libby humped each other every night thereafter before they fell asleep. Libby was soon experiencing orgasm after orgasm with her crotch pressed hard against her brother's, though she had no words for the intense feelings she was having. At first they rubbed against each other while wearing clothes, which was pleasurable enough. Then they began experimenting with grinding against each other whilst both were naked.
Once the twins began humping each naked, penetration was essentially inevitable. The first time Mark's small shaft sank into into his sister's tight pussy was of course unintentional -- and incredible! Libby's gash had just been so particularly juicy on this occasion, as the twins had recently begun practicing kissing each other all over. Of course as Mark kissed his way down his sister's body, he'd paid particular attention to her bald cunt mound and pink pussy flesh. By the time he was done licking and twirling his tongue all over her tiny clit, Libby had orgasmed on his face -- she loved when he kissed her all over! Her pussy lips glistened in the light of their room when he took his lips away.
Then Libby returned the favor, kissing all up and down her brother's shaft and sucking the head of his cock like a lolli-pop. Mark groaned at the feeling of her lips enveloping the hard head of his prick. It was maddeningly pleasurable. Finally Mark pulled his sister onto his lap as he sat on the floor. They kissed each other some more. Mark's small prick was pressing into Libby's slick cunt flesh as they embraced tightly. He ran his hands up and down her body and over her small nipples, making her flesh break out into goosebumps. His light touch along her ribs made her giggle.
Libby began grinding against her brother's naked crotch, gently bouncing in his lap. They humped at each other for a few minutes before his cockhead parted her pussy lips, and suddenly penetration was imminent. Libby gasped, feeling her brother's prick opening up her tight hole. Neither could explain it, but this feeling was definitely different than any other time they'd played around... As if overtaken by some powerful primal instinct, Mark bucked his hips upward to impale his sister on his cock. Libby let out a soft moan in her brother's ear, her arms wrapped around his neck. She closed her eyes, feeling herself filled up with Mark's cock meat. It felt strange, but so, so incredibly good!
They were having sex, making love even, although neither really even knew it. Mark loved the sensation of his sister's ten year old pussy squeezing his little member. Libby loved having her juicy pussyhole filled up! It was the most wonderful feeling either sibling had ever experienced thus far in their lives. Since Mark was still too young to ejaculate, he lasted for a long, long time. Libby bounced wordlessly upon his cock for nearly an hour, their lips meeting every so often in a passionate kiss until Libby finally orgasmed with her brother's cock inside of her young womb. She shuddered in his lap, their hearts pounding hard, as his slick shaft fell out of her juicy hole with a sucking sound. They stared at each other in awe.
And so despite being so young, the twins experienced intense love and passion normally reserved for adults. They were so appreciative of sharing this overwhelmingly amazing pleasure together that it strengthened their love exponentially. Mark penetrated his sister nightly, letting her ride to orgasm on his cock. It was all each sibling looked forward to throughout the school day -- that moment after their parents went to sleep, when Libby would crawl down onto Mark's bunk and began kissing him all over. They soon enjoyed experimenting with a multitude of positions -- Libby was quite flexible and gymnastically inclined!
Their parents delighted in how well the twins got along, at how mature they seemed to be already. They seemed to be growing up so fast! In reality, they were having sex before they even knew what sex was. Mark craved the feeling of his small prick slipping inside his sister's tight slit -- it was incredible! And Libby loved having her pussy inundated with cock flesh. The siblings were obsessed with each other, though they admitted it to no one. Even as the twins grew older and entered Junior High School, they insisted on sharing a bedroom. Their parents thought nothing of it. They knew twins were known to have a very close, special bond.
It was around the time they entered Junior High when Mark began ejaculating inside his sister. Their "hugs" had only become more and more pleasurable over the years since they'd begun experimenting back in their kindergarten years. Libby was surprised the first time she noticed the creamy fluid oozing out of her slit; she thought it was her own pussy juices. Then one night, eleven year old Mark took his twin sister's hand and helped her jack his cock to orgasm. He wanted to show her how his cock could now explode! Libby pumped her brother's erection until he gasped, his shaft throbbing in her hand. Her eyes widened as white ropes of cum spurted from the head of his cock all over her chest. They had no words for it, but it was amazing.
By their twelfth birthday, Mark noticed his sister's breasts beginning to grow. Her nipples enlarged and puffed out, forming small, succulent mounds. Libby did gymnastics after school, keeping her figure trim, tanned, and flexible. Mark also couldn't help but notice his sister's pubic mound wasn't as bald anymore. A thin patch of golden pubic hair was growing. He found himself even more attracted to her. Libby also thought her brother was growing into a handsome young man, and she admired his growing muscular physique, spiked dirty blond hair, and bright blue eyes which mirrored her own. They shared a strong, passionate love, far stronger than most siblings' love for one another. The twins didn't hang out with any kids from school; they were obsessed with each other.
They'd heard about sex, but only brief mentions of it that they never understood. And so it wasn't until 6th grade, in sex education class, when the twelve year old twins realized what they'd been doing every night. First, the boys and girls were separated to watch movies about the bodily changes they would experience in the coming pubertal years. After the movies finished, the boys and girls gathered back together again in the classroom and the teacher continued with the lesson. The students had never been so quiet, sitting at their desks paying rapt attention. Libby was pale. She nearly fainted when the teacher finally began discussing where babies really come from.
Mark was stunned to learn he'd been having sex with his own sister, though the knowledge didn't deter his ardent feelings for her. In fact, his prick twinged a little during the lesson when the teacher was talking about the male's sperm impregnating a female. His thoughts drifted away. He wondered if Libby was fertile. Had she become a woman? Was she ripe? The sex education class only made him horny. His balls ached to unload inside of his sister's womb as soon as possible -- it was such a powerful, addictive feeling. Being inside her made him feel like such a man. Filling her pussy with his hard meat, inundating her hole with his semen, making her take it all, listening to her moans and the slapping sound of naked skin on skin...
The twins learned "sperm" was the technical term for the sticky white fluid that Libby had seen bursting forth from Mark's cock. Those intense, electrifying waves of pleasure she felt nightly were called "orgasm." Then the teacher touched on some taboo topics, including brief mentions of rape and incest. Mrs. Horowitz stiffly read the definition of incest from her teacher's book: "The crime of sexual intercourse between relatives." Libby was mortified -- they'd been committing a crime every single night! And she could get pregnant if they continued having sex! She could have an incest baby! What if someone found out what they'd been doing?!
Mark's thoughts remained elsewhere during the rest of the day's classes. In his head, he was playing back tawdry scenes of his nude sister bouncing up and down on his rigid pole, or bending over and taking his cock from behind, or sucking on his prick. Now all these actions and parts had names attached to them: Penis, ejaculation, copulation, vagina, sperm, insemination, impregnation! The sex ed class had been a cold, hard realization of their very adult activities. While Libby left the class looking ashen and aghast, Mark was aroused. He'd been penetrating Libby for too long to give it up now! Honestly, it even turned him on to know his sperm could get one of her eggs pregnant with his child!
After school, Libby skipped gymnastics practice and ran home to the bedroom she shared with her brother. By now they'd traded the bunk beds for two side-by-side, full-sized beds. Twelve year old Libby burst into tears as soon as she closed the door. She looked around the room, from the beds to the dresser to the beanbag chair. She'd been fucked everywhere -- her brother had incestuously inseminated her not just in their bedroom but all over the house! Mark ran home after her sister, noticing she'd left school in a huff and skipped gymnastics. He ran into the house, stampeding upstairs and flinging the bedroom door open breathlessly, demanding to know why she was so upset. Libby sat on her bed, face in her hands. Her long blond hair fell around her shoulders in frizzy waves. She looked up at her handsome twin brother, her blue eyes filled with emotion.
"What's wrong, Libs?" said Mark.
"What do you mean 'what's wrong,' you idiot?! We're committing incest, a crime! You heard the teacher!" Libby shrieked.
"Libby, calm down, shh --"
"You could get me pregnant if we keep having sex!"
"Libby, quiet down! Well, we can -- "
"Having sex with the person I love is a crime!" she blurted.
They both grew quiet. Mark stepped closer to his sister, looking into her eyes as they overflowed with tears. Her cheeks were ruddy, her lips red. He thought she'd never looked quite so beautiful. Libby sniffled, staring back at her brother. He took her face in his hands, admiring her rosy cheeks and pouty, quivering lips. Then he bent down and kissed her, and she pulled him into a tight embrace. Libby's crying began to ease. Finally Mark pulled back. He smiled at his twin sister.
"Libby, what we learned in school today shouldn't change the way we feel about each other. You know I love you, too," he said. Libby couldn't help but smile. Her brother was always so sweet and knew just what to say to cheer her up.
She glanced at the clock -- they had about a half hour before their parents would be home from work. It was enough time for Mark to push Libby down onto her back on the bed and eat her pussy out vigorously to two orgasms, then for Libby to suck her brother's hard cock meat a few minutes before he laid her on her back and penetrated her slow and hard for several minutes. Mark's pace intensified as his climax neared. He looked down at Libby's slender body in the waning afternoon sunlight, his eyes fixating on her tiny, hard nipples upon her growing breasts. Mark grunted, his nuts tightening. His eyes met hers.
Libby moaned, feeling Mark's shaft pulsating inside of her. She knew he was flooding her hole with his semen, copulating with her, inseminating her womb, filling her up with his sperm! He groaned, his prick erupting inside his sister's cunt. Then Libby gasped when they heard the sound of a car door slamming outside -- it was probably their mom! Hot drips of cum oozed out of her hole and down to the sheets below as Mark abruptly pulled his prick from her moist, silky depths. Libby didn't have time to clean up before dinner was spread out on the dining room table downstairs. As she sat at the table quietly enjoying the take-out meal her mom picked up on the way home, Libby shuddered when she felt Mark's cum dripping out of her pussyhole and down her thighs. Her thoughts flashed back to minutes earlier when Mark unloaded that copious deposit of semen inside her womb.
"Do you like it, dear?" asked their mom, Louisa, all of a sudden. She was staring at Libby expectantly. Her mom's abrupt question shook Libby from her reverie.
"Huh, wha-what?" stammered Libby.
"Do you like it?" Louisa asked again, furrowing her brow.
"Like what?" Libby asked. The cum continued oozing from her hole, the crotch of her panties completely saturated.
"The meal, honey. Do you like the food?"
"Oh! Oh, yes. It's very good, Mom, thanks..." said Libby nervously, crossing her legs tightly. She worried the cum leaking from her pussy was going to leave a wet spot on the chair!