Poking her head out of her room, Twilight carefully peeked down the corridor. Looking down the length of the hallway, ensuring she wasn’t being spied upon, she crept outside and quietly pulled the door closed behind herself. She doubted there’d be many guards patrolling the castle, given the extremely late hour, which would make sneaking about all the more easy.

It’s been months since she’d taken a trip to the Crystal Empire, having kept herself busy with the aftermath Cozy, Tirek, and Chrysalis had left in their wake, and she desperately wished to see her bbbff again. For a typical visit, there’d be no need to surreptitiously tiptoe through the palace, but she’d had something special in mind for her evening.

For time immemorial, ever since Twilight had budded into a young mare, she and her brother had forged a rather intimate relationship. What had started as a curiosity between the siblings, exploring one another’s bodies, had eventually blossomed into rather scandalous shows of amorous affection. Of course, as they’d grown older, the frequency of such instances grew rarer and rarer, especially after Shining got married, though they hadn’t stopped entirely.

If and when the brother and sister found themselves in proximity to another, it was almost a certainty that they’d disappear for some privacy. While their stately positions and/or relationships didn’t make such endeavors the easiest thing to accomplish, the effort was well worth the reward. They knew each other inside and out, from kinks to erogenous zones, so their times of intimacy were unparalleled.

Softly sauntering through the hallways, sheathing herself in an invisibility spell, Twilight made a beeline towards her destination. Since Cadance was away on official business, meeting with the Yaks in the north-lands to broker a trade deal, she’d have Shining all to herself for the night. With only the palace staff to consider, the likelihood of being discovered was minimal, though she still moved as stealthily as possible.

Reaching her brother’s chamber, she hastily slipped inside and out of view. The room, while nearly pitch black, wasn’t too difficult to navigate. Though she was almost blinded by the darkness, she managed to make it to the bed. As her knees graced the edge of the mattress, she carefully leaned forward and rested a hand onto the padded surface.

Shining had told her that he had patrols that afternoon, which had given Twilight an idea. Secreting herself into his room, she had every intention of giving him a warm welcome after his shift. Pausing, she sat back and pulled her shirt upwards. Dragging the garment over her torso, flinging it into the darkness behind her, she unzipped the side of her skirt and let the garment fall around her knees.

In a matter of moments, the alicorn was wearing nothing but her birthday suit. True, she’d planned for the event by going without undergarments, but that had been part of her machinations. They wouldn’t be needing clothes, given what she and Shining would be doing, though wearing a shirt and skirt through the castle was necessary.
Now fully nude, Twilight lifted the blanket and crawled beneath it. She had to admit, even for royalty, Shining and Cadance had one of the largest beds she’d ever seen. Making her way towards the center of the oversized mattress, her fingers grazed something warm and furry. She froze, startled by the unforeseen development.

Shining hadn’t told her exactly when he’d be returning to his room, so she was left to assume he’d lied in wait for her. Grinning to herself, she massaged what could only be a thigh. While unexpected, the development was a pleasant surprise. Shuffling closer, caressing his hip and waist, her hand drifted towards his groin. Sure enough, she soon felt the warm, velvety length of his stallionhood.

Twilight couldn’t help but giggle, as her digits danced over the base of his shaft. While her hand wandered up his semi-rigid length, she gave it a little squeeze. It had been so long since they’d last fooled around that she’d nearly forgotten how big he was. Giving his length a few cursory pumps, cursing herself for not remembering how deliciously thick his tool was, she moved her face closer - then, in a dramatic turn of events, everything went awry.

The covers flew up and the lights flicked on, leaving Twilight exposed and blinded. Shielding her eyes, she reared up and nearly toppled backwards. Blinking rapidly, clearing her vision, she looked around to take stock of her surroundings. The room was exactly as she’d expected, with one glaring exception. There, sitting in a chair beside the bed, was Shining Armor.

Twilight’s mind went into overdrive, while it attempted to process everything that was happening. Her brother was was naked, lashed to a wooden seat, with a ball gag securely fastened to his muzzle. Looking lower, her eyes settled on his flaccid stallionhood; its size was precisely as she’d recalled, sending a cold chill of realization through her. If Shining was in the chair, that meant…

Her head whipped round, as she flew into a panic. Lying atop the bed, not but a few inches from where she rested, was none other than Princess Cadance. The heavily lidded, orchid colored eyes of her fellow alicorn peered up at her. Gazing down the woman’s body, past her rather substantial chest, her eyes went wide. As inexplicable as it was, a long, dark, and wonderfully girthy stallionhood was affixed to her sister-in-law’s groin.

Shocked, frozen in place, Twilight was at a loss for words. There were a great number of conundrums with the situation in which she found herself, so she attempted to digest everything. The largest issue was that, despite having a canoodled with her brother for ages, the Princess of Love knew nothing about it. Secondly, Cadance had a cock - and a damn nice one at that - which was utterly baffling.

Gnawing her lip, looking back and forth between her brother and the alicorn, she wasn’t sure what to do. Not only had her plans for the evening been well and thoroughly foiled, but she’d discovered that the mare who once babysat her had an absolutely prodigious tool. Trying to make sense of it all, she flinched, as something gently patted her thigh.

“Bet you’re trying to figure all this out, huh?” Cadance mockingly asked, affixing her with a sorrowful look. Slowly moving her hand from Twilight’s leg to her floppy length of Princess prick, she began stroking herself off. “To answer a few things I know you’re wondering - no, I haven’t always had it; but after I found out what you and Shining had been up to, I simply had to see what all the fuss was about. After all, if you’re good enough to cause my dear, sweet husband to go sneaking around, how could I not give you a whirl…”

Twilight gulped, as she watched Cadance’s stallionhood steadily grow to full mast. Even without being fully erect, the damn thing dwarfed her brother’s little soldier. An angry vein snaked under the violet flesh of the shaft, tracing the length from trunk-like root to blunt tip. Truly, it was equipment fit for an alicorn, but that wasn’t even the best part.

Beneath the Princess’ dick sat a pair of swollen, ripe nuts; each was roughly the size of a grapefruit, storing what had to be close to a liter of spunk within. Twilight’s mouth started to water and her marehood moistened, as she imagined how productive Cadance would be. Distracted by her thoughts, she didn’t notice the alicorn reaching for her groin.

“Since you seem interested,” Cadance began, running one finger up Twilight’s thigh, “feel free to experiment…”

The notion of empirical science did nothing to help Twilight’s disposition. It was bad enough that she’d abstained from any masturbation for nearly a week, before her trip to the Crystal Empire, so the added taunt served as yet more temptation. Looking to her sibling, seeing the pleading look in his eyes, she peered lower. His turgid stallionhood - more of a colthood, compared to Cadance’s unit - stood rigid. Even if he was bound up and forced to watch, he was clearly turned on by what he saw.

“Shiny, do you want to watch me breed your sister in front of you?” the Princess of Love purred, glancing at her husband. “If you’re a good boy and don’t cum, I’ll let you get sloppy seconds.”

While the stallion shamefully averted his gaze, his turgid prick visibly twitched. The last thing he’d expected that day was to be hemmed up by his wife - who’d bequeathed herself with an absolutely mammoth member - and bound to a piece of furniture to be cucked from fucking his sister. Confused and disgusted with himself, there was no denying the entire situation was kind of hot.

Twilight shivered, as Cadance’s digit glided over her quickly engorging sex. Swallowing hard, with her eyes locked on the alicorn’s dong, she reached her breaking point. Giving in to temptation, she closed her eyes and leaned over; after all, it would be rude to turn down the opportunity to bond with another Princess.

As her snout wandered towards Cadance’s nethers, her nostrils were beset by the most intoxicating bouquet she’d ever smelled before. Earthy, rich, and floral, the combined notes of a virile stallion and fertile mare accosted her sinuses. Breathing deeply of the alicorn’s aroma, her pace quickened, until her snout was pressed firmly to the love Princess’ weighty testes.

Burying her muzzle in the musky nexus, directly between the base of Cadance’s cock and her fat nuts, Twilight inhaled through her nose. Her sex clenched angrily, as if sensing the ambrosial scent, pining for attention. Sweet Celestia, she’d never encountered something so sinfully captivating. Without wasting any time, she dragged her tongue up the dickmare’s length, allowing her to get the first glorious taste of the alicorn’s flesh.

“Mmmmm,” Cadance hummed, closing her eyes and delighting in Twilight’s ministrations.

She’d had an inkling about her husband and sister-in-law’s taboo shenanigans for quite some time, although she’d only gotten evidence a few months prior. All it had taken was for the Equestrian Empire to nearly fall. After defeating the trio of villains in Canterlot, while everyone was busying themselves with cleaning the city of debris, she’d happened upon the siblings in a remote alley.

Twilight had been fellating her brother with reckless abandon, as she unabashedly got herself off. Caught off guard by the scandalous display, yet intrigued and slightly aroused, she silently watched them sate each other. The incestuous oral eventually transitioned into a rough fucking session, as the siblings rutted like lustful youth; it was in that moment that the seeds of her sweet revenge took root.

Instead of interrupting their little moment, Cadance had opted to scheme. It wasn’t all that hard, considering the two periodically made trips to see one another, though it did require a bit of preparation. Finding a spell to equip herself with a fully functional package had been the first step, while waiting for an opportune time to enact her plan.

As the weeks passed, she grew increasingly impatient. Eventually, having reached a breaking point, she’d informed her husband and the castle staff that she was going to meet with the yaks about a trade agreement. Tying him up and placing a negation ring on his horn had been easy, since she’d done so on the pretext that it was foreplay. The bait had worked perfectly, luring Twilight to the Crystal Empire and bringing them to that very evening.

A muffled moan snapped Cadance back to the present, as Twilight lipped and lapped upon the tip of her shaft. She was a bit surprised with just how easily the Princess of Friendship had folded; but, then again, she knew next to nothing about the alicorn’s sexual preferences. Content to let the blowjob begin, she looked over to her bound husband.

Immobilized as he was, Shining was left to watch the event unfold. Powerless to stop his sister, his stallionhood jerked and stood as a testament to his wanton thoughts. As badly as he would’ve loved to jump in, there was no denying how hot the sight of his wife and sister was. Left to hope he’d get released, if only to get himself off, he quietly tested his bindings.

Relaxing her jaw, Twilight slipped the head of Cadance’s marecock past her pouting lips. Such a magnificent specimen demanded her full attention - well, mostly. Wriggling in place, raising her waist, one hand crept down her body. While massaging her sex, she stroked and fellated the alicorn. Even if she didn’t end up getting a cunt full of Princess pony dick, she was going to enjoy herself.

“Sweet Celestia, she’s a horny little cock sucker! Did you teach her this, Shining?” Cadance giggled.

Though she’d only had a dong for a perilously short period of time, she quite enjoyed the bit of girthy anatomy. Not unlike an oversized clit, the organ was delightfully sensitive and, in her opinion, more than fun to play around with. Digging her fingers into Twilight’s hair, she applied a just a touch of pressure to the mare’s head.

Pumping the base of Cadance’s length with one hand, Twilight fully committed herself. Working the underside of her fellow Princess’ member, she knew there’d be no way she could throat the whole thing, though she was hellbent on giving it her best effort. Sinking to fingers into her marehood, she shamelessly rubbed her g-spot.

Bobbing her head, twisting it from side to side, she did her best to service the monstrous appendage. It was, by no small margin, the largest fuck-stick she’d ever tangled with, which presented a number of issues. She hoped, as she slobbered and sucked upon the pillar of flesh, her nethers would prove more accommodating, since she was struggling to fit more than a few inches in her maw.

Cadance’s hips reflexively bucked, sending the tip of her stallionhood to the back of Twilight’s throat. The smaller mare recoiled, gagging slightly, although it only served to get her more worked up. Even if she was still getting accustomed to the new bit of anatomy, she was more than interested with exploring every facet of the thing. Releasing the young Princess, restraining her lustful urges, she waited to see just how her friend would react.

Rearing back to her haunches, coughing slightly, Twilight wiped her face. Having just gotten her first delicious taste of cloying, salty pre- cum, she pined for more. Looking up to Cadance’s face, while continuing to knead and rub her heated snatch, she smiled sheepishly. As much as she wouldn’t mind making another attempt to fellate the alicorn, her loins yearned to be filled.

“S...so - uh - do you wanna…” she trailed off, hoping the older mare would catch her drift.

“Want to what?” Cadance countered, fully aware of what her friend desired. If the incestuous Princess wished to be rutted in front of her brother, she was going to have to beg for it. Idly cranking her shaft, she delicately gyrated her hips and waited.

“O...Oh, you know…” Twilight stammered. Releasing her crotch, blushing heavily, she crudely simulated an insertive gesture with her hands.

“Come on, Twilight, use your words!” Cadance chided, glancing down at her tool. Peering at the battering ram-like head, she was struck with an idea. “If you don’t have any suggestions, I might have to do it myself…” she whispered. Craning her neck downward, while angling her shaft towards her face, she leaned in and gave the tip of her dick a kiss.

Twilight and Shining stared in open awe, as the Princess of Love started suckling the end of her behemoth member. The stallion’s efforts to escape doubled, though the restraints held firm. His sister, however, wasn’t in such a predicament. Wheeling around, the plucky purple pony bent over, pressed her chest to the mattress, and wantonly presented herself.

“Just fuck me already!” Twilight demanded, scrunching her snout in consternation.

Cadance’s motions came to an abrupt end, as she looked at the svelte purple rump before her. With her tail held to the side, the smaller alicorn’s meaty and painfully wet marehood winked invitingly at her. Pushing herself up and abandoning her auto-fellatio, drawn by the siren’s call to sink her length into the nubile female, she shuffled forward on her knees.

Shining’s eyes flicked from his wife to his sister, as the two Princesses drew closer to one another. Jacking herself off, Cadance brought the drooling head of her cock to Twilight’s entrance. Positioned as he was, he had a damnably perfect view of the impending action. As soon as the dickmare’s regal member grazed his sibling’s entrance, a gout of pre-cum escaped his stallionhood. It was, without a doubt, one of the hottest things he’d ever seen.

Prodding Twilight’s entrance, Cadance slapped the mare’s ass. “You ready for a real dicking?” she snickered, forcing herself not to proceed.

The provocation, feeling the bloated head of her former foal sitter’s tool grace her sex, proved too much to bear. Reaching back, clasping one pillowy glute in each hand, Twilight prized her buns apart. If the dickmare didn’t get that hint, so help her, she’d take matters into her own hands.

Seeing Twilight debase herself flipped a switch in Cadance. Sinking her fingers into the smaller alicorn’s waist, she drove her hips forward. The slender Princess’ entrance resisted her efforts, leaving her shaft to bow slightly. Undeterred, grunting in frustration, she applied additional force. Harder and harder she pressed, feeling her mate fidget in her grasp, until it happened.

With all but an audible pop, nearly the first third of her length burrowed into Twilight. Both alicorns gasped, each unprepared for the sensations the other afforded. Giving herself a moment to relish the sublime heat and snugness of the marehood embracing her stallionhood, her mind desperately sought to comprehend the newfound pleasure accosting her.

Handjobs were pretty nice, the lackluster blowjob was better, but - by Celestia - sinking her member into a succulent marehood was, by far, the most divine thing she’d ever felt. Peering downward, slowly withdrawing herself, she watched Twilight’s meaty lower lips cling to her fleeing length. Halting just shy of pulling out entirely, she thrust forward once again.

Twilight, having released her tush, hastily grabbed a pillow from beneath the headboard. The abject feeling of fullness, of her canal stretched around the supremely thick alicorn cock, was damn near overwhelming. She considered herself fortunate, since Cadance had only just begun humping, though she knew she’d need something to stifle herself. Fetching the cushion and placing it under her head, she rocked back to meet her paramour.

Steadily pistoning her hips, Cadance delved deeper and deeper into the mare below. Inch after inch, her dick disappeared into Twilight’s velvety confines. Only when her medial ring bumped against her friend’s stuffed entrance did she meet additional resistance. Undeterred, yearning to fully entomb her length, she ground forward.

Sensing the astonishingly girthy ring of flesh pressing against her snatch, Twilight realized what she had to do. Slipping one hand beneath herself, she quested for the one thing which may aid her efforts. As her fingers graced her clit, a bolt of pleasure coursed through her. Even if Cadance couldn’t go balls deep, the additional stimulation would add another layer to the experience.

A muffled noise drew both the alicorns’ attention away from one another. Looking over, their eyes settled upon the bound stallion at the bedside. Cucked husband/sibling or not, neither of them had any intention of stopping - at least, until they’d been thoroughly satisfied. Looking Shining in the eye, savoring the pleading look he held, Cadance steadied herself, grinned, and started to fuck.

“Oh buck…” Twilight groaned, gnawing upon her pillow. Though the dickmare hadn’t fully hilted, her body lurched forward with each thrust. Toying with her clit with one hand, while tweaking and twisting one nipple with the other, she surrendered herself.

Cupping one bosom, Cadance’s gaze never left her husband’s face. “Enjoying the - Mmmph - show?” she grunted, pounding the unicorn’s sister.

Gagged as he was, all Shining would manage was an unintelligible protest. In truth, he wasn’t that upset about the turn of events - no, his frustration came from being unable to do anything but watch. Hell, he wouldn’t complain if he could jack himself off, but even that small joy had been robbed from him. The sights and sounds of his sister and wife pleasuring one another was maddening, yet it paradoxically cranked his arousal to unimaginable heights.

“Maybe when I’m - Unf - done, I’ll let you two fool around a little - after you lick my cum out of her, of course,” Cadance snickered, punctuating her statement with a particularly forceful thrust. “Isn’t that right, Twi?”

“Yes!” Twilight squealed. She had no idea what her fellow Princess had said, though it mattered little. In that moment, the only thing she cared about was being impaled by the glorious fuck-stick within her. Gyrating her waist and arching her back, she pushed herself backward.

The submissive display drew Cadance’s attention back to the task at hand. Retracting a few inches of her tool, firmly grasping Twilight’s hips, she drove forward with all her might. The insanely thick lower portion of her stallionhood bludgeoned its way inside of the mare, causing her waist to slam against her mate’s ass.

Spontaneously, without any warning whatsoever, Twilight came. Her body simply wasn’t accustomed to such a monumental intrusion nor had her womb ever been so thoroughly crushed before. Crying out, spraying orgasmic juices from packed cunt, she trembled from head to toe. Somehow, despite having suffered through a cataclysmic climax, she continued eagerly rubbing her clit.

“Bet you’ve never made her cum like that,” Cadance condescendingly purred to herself, reminded of witnessing her husband fucking his sister in the alley.

Though Cadance was purely focused on the shivering mare beneath her, she was compelled to add the small insult. While she had no intention of stopping the siblings from fooling around, she was going to make good and damn sure that Twilight would be well and truly tainted by the experience. Steadying herself, pulling out all the stops, she started jackhammered the alicorn.

Under the full brunt of Cadance’s carnal assault, Twilight’s world was nothing but blinding pleasure. Every fiber of her being screamed with bliss, threatening to overcome everything she’d ever known. She was, in a very real sense, losing herself. If she’d known that an alicorn, and her sister no less, was capable of bringing her to the heights of ecstasy, she would’ve gone to the Princess far sooner.

Like some great, primal deity, Cadance pounded her mate from behind. Through some combination of arousal and sadistic glee, at foiling the sibling’s incestuous plans, the speed and force of her bucking hips magnified - but that wasn’t all. Draping herself over Twilight’s back, she seized the mare’s mane.

“Tell him what you really want,” she growled, pulling the young Princess’ face away from the pillow.

At the abrupt change of pace and titillating trace of discomfort, something broke within Twilight. “Breed me! Make me your slutty little mare!!!” she brayed, feeling the approach of yet another mind-bending climax.

The request sent Cadance into a frenzy, teasing parts of her she didn’t know she had. Fucking for all she was worth, she drove the mare forward. Twilight’s knees gave, leaving her to crash fully onto her stomach, yet that did little to deter the Princess of Love. Adjusting herself ever so slightly, she continued to pound away.

Utterly at her sister-in-law’s disposal, Twilight was in heaven. Lying there, being fucked like some wanton harlot, she was at a loss for words. The experience, beyond being incomprehensibly enjoyable, was eye opening. If dickmares were capable of delivering such inconceivable rapture, she may need to give up stallions all together. Whimpering with every thrust, feeling her clit being slapped by Cadance’s pendulous nuts, she welcomed her role with open arms.

Angrily grunting, Cadance knew she was reaching her limit. As badly as she would’ve liked rutting Twilight until daybreak, she realized it would be impossible. Pummeling the mare’s fertile womb, the resistance around her length increased. The tip of her cock flared, swelling to virtually double its original size, as her testes pulled to her groin.

With a bestial roar, she came. A veritable tsunami of scalding, virile seed rocketed through her stallionhood, causing it to throb violently. Hilting every inch of herself within her mate’s confines, ensuring every drop of potent spunk was deposited as deeply as possible, the floodgates burst.

Twilight’s eyes rolled to the back of her head, her heart fluttered, and her mind went blank. Under the influx of so much cum, bathing her cervix and interior, she suffered a second cataclysmic climax; much like the first, the second was indescribable. Mere words couldn’t describe the earth shattering pleasure of being bred in such a debased manner.

With her toes curling, enrapt by godly bliss, her consciousness faded. Mortals, alicorn or otherwise, simply weren’t capable of experiencing ecstasy of that magnitude, so her body conceded. Her limbs went limp, as she slipped into the warm embrace of darkness.

Pushing herself up, Cadance wiped a strand of drool from her chin. Having sated her rut-lust, some modicum of mental clarity returned. Although Twilight had been taught her lesson, she wasn’t quite finished. Getting to her knees, she hauled her unyielding dick from Twilight’s sex.

Situated as he was, Shining bore witness to the eruption of jizz from his sister’s marehood. An initial gout of the viscous substance spattered his wife’s thighs, while a second and third spurt thoroughly covered Twilight’s rump, thighs, bed sheets, and anything else within the splash zone. He was so engrossed with the debaucherous geyser that he almost didn’t notice Cadance getting to her hooves.

Sauntering over to him, the dickmare’s length swayed from side to side; glistening with spunk and mare-cum, nearly as large as his forearm, it came to rest not but a few inches from his muzzle. Peering up, meeting Cadance’s eyes, he saw the perverse smirk she wore.

“Lick it clean…” she commanded. Without waiting for a response, she smeared his cheek and snout with her cream and his sister’s nectar. Reaching down, she unclasped the gag around his head.

Cadance smugly watched, as her loving husband did as she’d asked. Dragging his tongue over her shaft, mopping it of every trace of foal batter and Twilight’s essence from her cock, she ignited her horn. With but a thought, she undid his bindings and removed the negation ring from his horn - still, freed though he was, he didn’t move.

It was only when she noticed his loins, spattered with his own ineffectual load, did she realize what had happened. At some point, he’d spontaneously ejaculated to her and Twilight’s little show. Filing the information away for future use, she laughed at just how pathetic he was. She loved him, that was for certain, though he’d clearly lost a touch of respect in her eyes.

“I’m going to take a shower. Put yourself to good use and dig every drop of my seed from your sister’s cunt with your tongue- if you do, I might let you get a round with her,” she chuckled, strolling towards the restroom.

Though she’d accomplished her goal, having simultaneously cucking her husband and sister-in-law, something nagged at her. There were a lot of benefits to rocking a dick, including not having to worry about getting knocked up or dealing with the mess of being creampied, though it wasn’t those. Imaging the looks Twilight and Shining had given her, it fell into place. With as undeniably fun and richly rewarding as the experience was, she might need to give them a follow up lesson in the future...