Sibling Rivalry

"Come on sis, just do it with me," Alice pleaded as she masturbated.

"Ugh no what's wrong with you? No Nut November is totally stupid," said her half-sister Sara as she too stroked her own dick. The two sisters sat across from each other virtually, each one facing the phone propped up at the end of their respective beds. Though they video called often, nothing sexual had occured between the two in quite a while, not since Sara had made things official with her girlfriend. Both had felt uncomfortable continuing their sisterly antics while one was in a monogamous relationship. That had changed recently when Sara got dumped, and the two quickly relapsed to their old ways.

"It's not stupid. You just can't do it because you're a worthless one-pump chump," Alice huffed angrily. She didn't intend to be so aggressive, yet she was.

"Fuck you, I am not." Several empty seconds went by. "The doctor said it's not that rare. He said it's my anxiety," Sara finally replied sheepishly. Despite being the younger sister, Sara far outshined both her sister and mother in the cock department. The three were all futas, but while her sister and mother were only carriers for the hyper gene, Sara's was activated. In addition to this, there had been a complication in her conceivement. She had been conceived by a one night stand with a well endowed futa, but her mother's pharmacy had mixed up her birth control with a prescription for an experimental, high grade fertility drug that contained trace samples of horse semen. So not only was she a hyper futa, but she had an equine cock. The thick, veiny shaft was white like the rest of her. Once she got hard, a pink, flat, ridged tip emerged from an equally veiny equine sheath. At full mast her bitchbreaker was two feet long, reaching up between her perky C cups and resting right below her collar bone. Two grapefruit-sized balls rested right beneath them in a tight sack. She had always been self conscious about it, having been bullied on multiple occasions for its unusual appearance. Though she had engaged in foreplay many times before (mostly with her sister), she had yet to lose her virginity. Her sister had been her only steady sexual partner, but penetration was one boundary the two sisters refused to cross. As a result, Sara had neither been penetrated nor ever penetrated someone. Her lack of experience and inability to fit comfortably in clothing (or someone's orifice) resulted in her being very quick to cum, which in turn also scared off many potential partners. Thanks to her excessive size, only girls looking to get their guts rearranged ever approached her. Most others had been scared off by rumors of her massive horsecock. Upon witnessing her abysmal stamina, their disappointment coupled with a fear of an accidental pregnancy usually meant Sara never got a call back afterwards.

"Sorry sis. I just think you should do it with me, even if I'm away at college. It could be fun, even if you totally lose. Let's put a wager on it."

"You're so annoying. Like what kind of wager?"

"Loser has to be the winner's slave for an entire month when I come home for winter break," Alice dared with a sly grin. Unlike her sister, she was merely a carrier for the hyper gene, like their mother. Her cock was only 10 inches, one above the average for futas. Her balls were above average, being the size of tennis balls, probably thanks to her unactivated hyper gene. She wasn't quite sure how big her mom was, but the three had once had too much wine during a family movie night and jerked off in front of each other after getting aroused by a cheesy sex scene. Though their mom acted like it never happened, Alice was sure her mom was a couple inches smaller than her. The rest of Alice's body resembled her mother's, albeit slightly less thick and milf-like. She chalked this up to the fact that their mom had already had two kids. Though their mom was much thicker, both Alice and Sara's bodies were much tighter and leaner. Alice sported a firm pair of modest D cups that sagged just a tiny bit on account of her constantly going out without a bra. She loved the effect that it had on men and futas, especially given that she preferred to wear tight, usually cropped t-shirts. Something about the way they couldn't take their eyes off of her boobs innate bounciness or how her hard nipples always poked through was addictive. Her ass was nothing to scoff at either. Thick and plump with just a hint of cellulite to give it some real bounce. She sported the perfect hourglass figure.

Sara gave her a frustrated look through the screen. Both of her hands had been running gently up and down her cock, spreading the steady trickle of precum across her majestic size. They stopped at her sister's request. Alice's hand continued to pump at herself as she waited for a response. She only stopped to spit on her girlcock before resuming.

"UUGGHH fine, deal. Just shut up and let's cum. I have homework to do." Sara's hands resumed their slow stroking. She could never keep up the same pace as Alice thanks to her 'condition'. Always wanting to cum together, the poor hyper had to slowly tease herself until Alice started displaying signs of an impending orgasm. As her sister started to breathe heavily, Sara began to jerk herself off rapidly. Her elbows moved inward, pushing her breasts up against her meat as it spread its all-natural lube onto them.

"Mmm I can't wait to beat you at this stu-stupid competition."

"Yeah?" grunted Alice. "You think you can?"

"... you're going to c-clean my sh-sheath every morning..." mumbled Sara.

"Uh huh," Alice said absent-mindedly as she felt a tightening in her balls.

"...w-with... your tong-AAHHH!" Sara cried. Her left hand moved down to play with one of her nuts, which in turn pushed her over the edge. A shocking orgasm ripped through her and cum began to spray out of her dickslit. It drenched her neck and chin before dripping back down. It rolled down her perky tits and began to ooze down her tip. Her sudden orgasm accidentally caused the hand on her nuts to instinctively tighten, forcing her to squeeze one of her nuts hard. The mix of pain and pleasure elicited a moan from her, and the pressure on her ball resulted in an extra fat rope of cum to plaster itself in a stripe across her pretty face.

The sexy sight of her half-sister hosing herself down pushed Alice over the edge with her. A plastic cup resided on the bed beside her, and she retained just enough mental acuity to remember to grab it and place it just below her tip. Though Sara's orgasms were understandably bigger, Alice's were nothing to scoff at. Rope after rope sprayed out into the cup as she groaned loudly. After thirty seconds, it tapered off until a little glob rested between the rim of the cup and the underside of her tip. Her dick gave a few last throbs as she finally stared back at her phone. Her sister lay back against her headboard panting heavily. Cum totally covered her upper torso. It ran down all over her boobs, with a couple strings hanging from her suckable nipples like ripe fruit. Some of it ran down her stomach. Though her orgasm had ended, a weak stream trickled out of her slit and down her shaft, pooling on her fat balls. Alice wanted nothing more than to lick away at the river of cum rolling down her sister's shaft until it was spotless.

"I hope you got it all out little sis, because tonight is October 31st. It's the last night we can cum for a whole month. Got about 3 hours left," she stated with heavy breaths.

Her sister panted some more. "If I don't fall asleep first I might fire off a couple more." Sara leaned her head down and began to lick her slimy cockhead clean.

"Mind giving me something to use for later? A little show ya know? Purely for scientific purposes," Alice joked.

Sara pulled her head up and rolled her eyes hard. She puffed her chest out for the camera, letting her softening dick fall down on the bed between her knees. Both of her hands reached up and began to massage her own cum into her tits. She sensually rubbed and squeezed them, enjoying the hot, sticky glaze seeping into her sensitive breasts. She toyed with her nipples too, pinching and pulling on them, before scooping up some of the cum pooled in the sack skin between her balls and pouring it into her mouth. The young futa swallowed most of it, but purposefully allowed some of it to roll down her mouth and face and drip down onto her chest.

"Oh my god you're so hot. Thanks twerp, I'm going to jerk off to that as soon as I beat your ass at this challenge. Then I'm going to abuse you all Christmas long." Her dick twitched at the thought.

"Whatever bitch. I need a shower. I'll see you later," Sara scoffed.

"Love you bitch."

"Love you too." The phone screen went blank as her sister hung up. Alice brought the full cup of cum up to her lips and began to chug. It was thick and milky like a protein shake. Alice much preferred it to an actual protein shake, as it was organic, free, and came with a complimentary orgasm. It was very useful for her gym sessions, and her overall health. She thought back on the No Nut November challenge, and wondered how quick it would take for her sister to get overstimulated and accidentally blow her load. Knowing Sara, probably not long. Alice couldn't wait to win.