“Whatcha reading, Twily?” Shining Armor queried as he flumped down on the couch, sending up a tiny puff of dust.

Twilight looked up from her heavy book with a smile. “Unicorn physiology!” she said excitedly, giving the smallest of bounces in place on the other end of the couch.

The two siblings were now old enough that their parents didn’t feel it necessary to hire a babysitter to look after Twilight when they left for the evening. This decision was much to the rue of Shining Armor, as he couldn’t spend time with Cadance. Or more specifically, he couldn’t take her upstairs to his room after Twilight was asleep and screw her into the bed.

It was only an hour into the evening, and the sun was barely going down, and already Shining Armor was bored.

“Anything interesting in there?” Shining Armor asked, ears perking upwards hopefully.

“Oh, nothing much really,” Twilight admitted, frowning slightly. “I know most of this already.”

“I’ll quiz you,” Shining Armor offered, snatching the book from her grasp and turning it around to peer at the page. His eyes widened slowly and his jaw dropped.

A cut-away image of an aroused stallion was splashed across the page, in perfect detail, with various informative tags pointing at the different parts of the gigantic cock and testicles.

Shining Armor’s eyes boggled.

Twilight arched an eyebrow.

“You’re… wow, Twily,” Shining Armor said, looking from the page, up to his little sister. “Why are you… looking at a giant picture of a stallion’s cock?”

“It’s part of the curriculum,” Twilight said easily, shrugging her shoulders slightly. “I learned the anatomy of a mare last week, which was easy considering I am a mare. But the stallion is harder because, well, there are no stallions around willing to let me study them.”

Shining Armor pondered on that for a long moment, looking down at the page, and then up at his sister. “...I’m a stallion.”

“I’m aware,” Twilight said, deadpan.

“Well, if you need to study a stallion for school…” Shining suggested, trailing off slowly, raising an eyebrow.

Twilight gave a thoughtful hum, mulling it over. “You’d let me study you?”

“It’d be my pleasure!” Shining Armor attested with an eager nod.

Twilight smiled brightly. “Sure, then!”

“Just ahhh… we should keep this to ourselves, some ponies might think it a little weird that I let you study me,” Shining Armor cautioned.

Twilight nodded once. “Yeah, that might raise some eyebrows,” she admitted.

Shining Armor grinned at that, sitting up straighter on the couch and then turning toward Twilight, leaning back until his back was pushed against the arm of the chair, pausing a few moments before spreading his hindlegs to reveal his thickened sheath to his sister.

A thoughtful hum left the unicorn, and she peered in at him curiously, leaning in to inspect him closely. “From the colour, I suspect that it’s black when fully erect?”

Shining Armor gave a nod. “Yeah, kinda black and grey.”

“Can you get erect for me?” Twilight asked, peering up at him with inquisitive purple eyes.

Pausing for a moment, Shining Armor gave a slow nod, a smile spreading across his muzzle. “Sure… sure… just give me a moment to think of something.”

One of Shining Armor’s hooves slipped down his form, rubbing slowly at the rim of his sheath, coaxing out the hidden flesh.

“Why don’t you think of Cadance?” Twilight suggested with a thoughtful hum. “She’s quite attractive.”

“She is,” Shining Armor said with a slow nod, staring down at his litter sister, eyes narrowing slowly. “Could you… lend me a hoof?” he asked cautiously.

Twilight blinked once, biting her bottom lip, looking unsure and nervous for the first time since they had begun. “I… I guess so,” she said after a moment, lifting a hoof to place over his own.

Shining Armor grinned, sliding his hoof away and leaning back, watching his little sister with avid eyes as her hoof came to rest on the swelling length of mottled black cock.

Peering in at his growing flesh thoughtfully, Twilight started to rub her hoof over it, gently tracing its lengthening contours. “it’s kinda spongy…”

“It gets harder,” Shining Armor said with an earnest nod, watching with interest as her hoof coaxed him out.

Twilight hummed to herself, sliding her free hoof down to heft his testicles, gently lifting each one. “Quite heavy…” she muttered to herself, the faintest of blushes spreading across her muzzle.

“Are you… sexually active, Twily?” Shining Armor asked after a moment, panting just faintly as his thick length grew and swelled into the touch of her hoof, quickly throbbing to full size.

Twilight nodded slowly, staring up at him.

“Do you… masturbate?” Shining Armor asked, eyes wide, panting faintly, his stiffened cock giving an eager throb as he asked the question.

Twilight nodded once more, but didn’t answer verbally.

“What do you think about when you masturbate?” Shining Armor asked, his hips shifting on reflex, even as a dribble of precum slowly spilled from the tip of his stiff cock.

“Stallions,” Twilight said quietly, stroking her hoof delicately up the length of his cock, tracing his medial ring, and then smearing the dribble of precum across the underside of his thick, spongy tip. “Big… throbbing penis’…” she whispered, staring at the stiffened cock, almost entranced. “You and Cadance…”

Shining Armor blanched at that. “W-what?”

Twilight nodded once. “You and Cadance. I watch you sometimes, when you think I’m asleep,” she said matter-of-factly.

A faint shudder coursed through Shining Armor’s form, and he gave a nervous chuckle. “I didn’t think you knew about that…”

“She is quite a skilled lover, isn’t she?” Twilight asked, tracing the length of her brother’s cock with her hoof. “I’m done here,” she said suddenly, pulling her hoof away.

Shining Armor almost whimpered. “D-done?”

“I’ve learned all I can,” Twilight said with a nod. “Thank you for showing me, Shiny.”

Shining Armor flailed a hoof. “N-no wait!” he panted, giving a strained sort of smile. “Don’t you want to… uhm…”

“Want to what?” Twilight asked, an eyebrow raising slowly.

“O-oh just get some.. u-uh… hooves-on experience,” Shining Armor said with an earnest nod. “After all… if you want to be as skilled as Cadance, then you’ll have to practise… practise makes perfect!” Shining Armor said with a strained smiled, his expression hopeful.

“You’ll let me stroke you to orgasm?” Twilight asked, giving him a long stare.

Shining Armor nodded eagerly. “Yes!” he said, before clearing his throat and looking away. “I mean, yes. Yes I will.”

“Well… it would be a good learning experience,” Twilight said, scratching her chin thoughtfully.

Shining Armor was already leaning against the arm of the chair, propped up on his back, hindlegs spreading wide, thick cock throbbing upright in his lap. “Use your tongue…” he said breathlessly, watching her with an avid stare.

Twilight arched a brow. “All in the interest of studies, right?” she asked dubiously.

Shining Armor nodded earnestly, his stiffened cock giving an urgent throb. “Yes, Twily. In the interest of studies,” he purred, biting his bottom lip as he watched her with interest.

Twilight seemed to shrug, leaning in with a curious stare, judging the size of his cock. “It’s much larger than I estimated,” she said thoughtfully. Shining Armor went to answer, before fading off into a gasp and shudder as his little sister dragged a warm, tentative lick against the underside of his cock.

“Like that?” Twilight queried, peering up at him for guidance, tongue extending to lap at him again.

Shining Armor nodded in earnest, biting his bottom lip again. “Y-yeah, Twily, just like t-that!”

Twilight gave a soft shudder of arousal as she lightly dragged her tongue up the length of her brother’s stiffened cock, nostrils flaring as she inhaled his scent.

“O-oh geeze, Twily, that feels good,” Shining Armor groaned, watching his little sister with interest, teeth baring just slightly as her tongue flicked off the underside of his tip.

“You taste strange…” Twilight said, working her jaw thoughtfully. “But I like it.” With a low purr, the young unicorn leaned in and closed her lips over the very tip of his cock, tongue pushing up against the round nub of his urethral process, grinding against the sensitive little expanse of flesh as she suckled wantonly.

Shining Armor gasped aloud, his hips shifting on instinct, ears splaying flat and a hoof flying to her head, brushing through her mane. “H-holy g-geeze…” he stammered.

“My books are very informative,” Twilight purred, delicately lapping at the tip of his cock, idly swirling her tongue around the glans, closing her lips over it to suckle again gently. A spurt of precum spilled up over her tongue, and she whimpered faintly at the taste, swallowing thickly.

Shining Armor groaned helplessly, his hips rocking back and forth against her motions slowly. “O-oh fuck, Twily, that feels good,” he groaned, hoof clenching in her silky mane.

“Better than Cadance?” Twilight asked innocently.

Shining Armor nodded in earnest. “Y-yes!”

Twilight smiled up at him, her expression turning mischievous. “I’ll let you… ejaculate in my mouth, if you return the favour…”

Shining Armor shuddered helplessly, swallowing thickly and staring down at his little sister. “Are you… are you getting aroused?”

Nodding slowly, Twilight gave another slow lap against the tip of his stiff member. “Yes. Very.”

With a lustful growl, Shining Armor rolled forwards, a hoof pushing Twilight away just slightly, before pressing down against her chest, slowly pushing her over onto her back.

Twilight blinked once, struggling faintly at first, before allowing her larger brother to push her onto her back, until she was almost flat. Tentatively, she slowly spread her hindlegs.

Shining Armor stared down at her, giving a low, lustful growl, his eyes falling on his little sister’s already-drooling, barely-mature cunny. With a quick push of his hooves, he lifted his sister’s entire lower body, pushing a pillow under her lower back to keep her leveraged, presenting her soft cunny his gaze.

The soft purple fuzz of fur that covered her entire body persisted even there, slightly damp now with Twilight’s arousal, covering the entire outer surface of her plump cunt. The faintest glimmer of pink flesh was visible between the soft purple lips.

Shining Armor shuddered, leaning in and inhaling, smelling the sweet scent of his little sister’s arousal, before he dragged a heated lick right against the soft expanse of the slick cunny. The heated taste of his sister’s arousal flooded his senses, and he gave an eager, lustful growl, digging his tongue in against her wantonly. A forehoof slipped up, wrapping around her lower back to rest on her side, squeezing and stroking back and forth just gently, even as he stared down at her over the smooth swell of her stomach.

Twilight stared up at him, biting her bottom lip, her back arching a little further on reflex, pushing her hips up towards the brush of her brother’s tongue tingling across her aching cunt so wonderfully. A slick dribble of her liquid welled up from within her, quickly lapped up by the omnipresent tongue.

An eager growl left the stallion, and he dragged his tongue against her all the more eagerly, pushing it firmly up against the soft lips of her sex, digging into the sweet crevice of her cunny to push against her inner flesh. His free hoof lifted, pushing at her inner thigh, spreading her open just a little with the pressure to let his tongue graze directly against the exposed soft, pink flesh.

Twilight arched under the touch of his tongue, groaning helplessly, muzzle parting in a heated gasp, a hoof reaching forward blindly to grasp at her brother’s horn helplessly, tugging him against her eager, clenching sex all the more firmly.

Shining Armor gave a lustful growl, panting heatedly against the plump lips of his little sister’s spread cunny, his nose pushed rather firmly up against her clit while his tongue ground against the base of her spread lips. With a smirk, he dragged a warm lick along the length of her drooling slit, to find her little clit at the apex of her cunny, closing his lips over it.

Twilight’s eyes widened and she stuffed a hoof in her mouth as she fairly screamed, her powerful thighs clenching around Shining’s head repeatedly as he suckled at her clit. Almost immediately, a slick dribble of her liquids spilled up against his muzzle, coating his chin in her arousal.

A soft chuckle left the stallion, and he idly suckled at her clit a little more, before pulling back to slowly swirl his tongue against the drooling slit of her cunny. “As you can see, I have studied extensively.”

“I concur,” Twilight muttered distractedly, blinking several times in a hazy fashion. “I’d give that a passing grade.”

“I can’t think of any good school puns, Twily,” Shining Armor admitted, releasing her rump and letting her fall gently to the couch, even as he leaned back and sat down once more, the stiff length of his eager cock bobbing up in the air. “But I really, really want you to finish me off.”

“I’m definitely ready to pass my oral exam,” Twilight breathed, purple eyes narrowing on the twitching length of her brother’s cock. She rolled carefully over onto her hooves, before dropping down onto her stomach and chest, pushing her nose right up against the midpoint of the thick length. “This isn’t weird, is it?”

“Sweet Celestia, no,” Shining Armor assured, stroking a hoof through her mane in encouragement. “I’m just helping you study for your test.”

“This seems a bit more intense than just some simple studying…” Twilight admitted, before shrugging inwardly and then leaning up to drag her tongue against the tip of her brother’s cock with an eager growl.

Shining Armor winced slightly in surprise and delight, spreading his hindlegs further to give his little sister the best access possible, panting down at her, watching with avid interest.

A soft giggle left the female unicorn, and she lipped delicately at the underside of his tip. “I haven’t seen you stare this intently since the first time Cadance took a bath with the door open.”

Shining Armor flushed just faintly at that, lifting a hoof to rest in her mane, even as his hips rolled against her muzzle, grinding himself against her lips heatedly. “Shush, Twily. You have studying to do.”

Twilight gave a derisive snort, trailing a hoof up the length of throbbing flesh. “I bet I could make you finish in record time…”

“This is hardly a race… but I would prefer you start sometime soon,” Shining Armor admitted with a slight frown, grinding against her lips pointedly.

Twilight giggled devilishly, one of her hooves unconsciously slipping down to push between her thighs, rubbing slowly over her still-drooling cunny as she spread her lips and then slipped her brother’s stiff cock between them.

Shining Armor gave an eager growl at that, watching with unguarded interest as his little sister stretched her jaws wide around his swollen cock, capturing his tip to suckle and lip at slowly. He leaned backwards with a soft, contented groan. “O-oh fuck, Twily, you have no idea how good that feels…”

Twilight nodded once, causing a slight dip over his cock and a swooping sensation in her brother’s stomach at the sensation. “I have some idea,” she purred around her mouthful, before smiling up at him.

Blinking curiously, Shining Armor kept his eyes on her own, watching as she smiled rather harder than usual, seeming to strain to keep the expression as she suddenly slipped down him far, far further than she had any time previously. His eyes widened and his back arched on reflex as his tip slipped down her throat, swallowed up by the intense tightness, and the soft, urgent tugging of his little sister’s convulsive swallowing.

Twilight shuddered, feeling her throat stretching around the thick length of cock, a whimpered exhalation brushing against the base of his flesh as she continued to smile hard around her mouthful, unable to stop the convulsive swallowing, but noting the way each firm tug of her throat muscles caused her brother to twitch and shudder.

“O-oh sweet Celestia!” Shining Armor gasped, his hindlegs twitching and kicking on reflex, his hoof grasping at her mane in a helpless scrabbling. Not even Cadance could do that!

Shuddering faintly, Twilight shifted her hoof to the base of his cock, working her muzzle back and forth for a few long seconds, before tugging back with a gasp for air, panting hard, tongue hanging from her muzzle, several strings of saliva hanging from her lips and tongue.

“T-that is a lot hard than the book said it would be,” Twilight panted breathlessly, cheeks flushed slightly with the exertion, before she leaned back in to suckle and lip at his tip almost playfully. “G-give me a moment to catch my breath.”

“You don’t have to keep doing that,” Shining Armor suggested, panting faintly as he watched her, his cock throbbing almost painfully. “Don’t hurt yourself on my account.”

Twilight peered up at him, grinning wildly. “But I want to get perfect marks,” she protested, even as she grasped the base of his cock again, and then shoved her muzzle back down around him. Almost immediately, her nose was buried in against the base of his cock, and purple eyes, eager for approval, were peering up at him from the bottom of his aching cock.

Shining Armor nodded urgently down at her, biting his bottom lip and then clenching his eyes closed. The image of his little sister deepthroating his cock and seeking his approval for the act was too much.

Twilight purred eagerly around him, a hoof wrapping around his hips while the other slipped down to idly play with her drooling cunny, even as she started to bob and thrust her head back and forth over the stiff length of his cock. Even few bobs, she would pull back to breath, panting faintly against the tip of his length, tongue idly lapping at the throbbing tip in between rapid panting.

“T-Twily,” Shining Armor warned almost urgently. “I-I’m getting close.”

“Will I get extra marks if I let you ejaculate in my mouth?” Twilight asked, perking up almost instantly.

Shining Armor clenched up at that, growling lustfully and grasping her mane in his hoof, eagerly humping towards her muzzle. “Y-yes! All the extra marks!”

Twilight gave a muffled ‘mrrfmph!’ of happiness, the hoof from between her thighs, slick with her liquids, slipping up to grasp around his testicles, squeezing gently while she bobbed along his stiff cock almost urgently.

Shining Armor shuddered, his eyes rolling back and a forehoof grasping at the back of the couch, while his other shoved hard into the cushion, giving a few firm humps into his little sister’s mouth as his eager cock stiffened and jerked wantonly.

Even with her foreknowledge from the textbooks, Twilight wasn’t quite ready for the explosion of eager, potent spunk that suddenly inundated her. One moment her brother’s flaring cock was spreading her jaws open, and the next, she was just drowning.

Burst after urgent burst of heavy, sticky cum spilled across her tongue, filling her mouth to overflowing almost instantly. Twilight swallowed on reflex, eye widening at the rich, heady taste of her brother’s arousal slipping down her throat in a thick, sticky stream. But then came the next burst, and the next, rapidly overwhelming the volume of mess she could swallow down. The young unicorn started to panic, patting at her brother’s hips with her forehooves helplessly as a thick dribble of his gooey mess started to drool and spill from the corner of her lips, meeting at the centre of her chin and trickle down the fur of her throat in a messy stream.

Shining Armor gasped heavily as he tugged backwards, a hoof rapidly stroking at his still-spurting cock, spilling several eager spurts across his little sister’s face. Twilight winced backwards, one eye closing as a line of mess spilled across her cheek and another caught across her muzzle. She shuddered, needing to breath, and opened her muzzle up with a whine of distaste, having to let a gooey streamer of her brother’s mess spill from her open mouth and drool to the couch as she panted heavily.

In a hazy afterglow, Shining Armor looked down at his little sister, catching sight of her, open-mouthed and panting, tongue and lips coated in his spunk, with lines of his eager emissions across her face and cheeks, staring up at him with wide eyes.

“Oh that has to be worth top marks, Twily,” Shining Armor said, before giving a helpless chuckle and a shudder of delight.

Twilight panted heavily, jaw working slowly as her brother’s taste inundated her senses. She closed her mouth, swallowing thickly, the mess in her mouth shifting down her throat in a visible lump. “I was not ready for that,” she admitted, lifting a hoof to wipe off her chin. “I’ll be ready for it next time.”

“N-next time?” Shining Armor squeaked, his eyes widening slowly and his tail starting to swish back and forth in anticipation.

“Well… I hardly passed the grade this time, did I?” Twilight asked, motioning towards her messy muzzle.

Shining Armor gave a soft laugh at that, scratching at his chin, a mischievous smile spreading across his features. “Well...y’know… you might need a few more private lessons.”

Twilight nodded with a slow smile, beginning to idly lick her hoof clean. “I intend to get full marks for my oral exam.”

Author's Note

This story may see a continuation in future, with more 'lessons'.