Celestia sat by her ornate mahogany desk, watching her younger sister pacing back and forth with an annoyed look upon her face. Celestia had told her about her plans for much needed vacation and that she would be placing her in charge of the kingdom for an extended period.

“We cannot believe you would do such a thing dear sister!” Luna demanded, “Surely you must give us a better explanation than that.” Celestia sighed at her impulsive sister.

“Is it really that hard to understand I need a break from all this Lulu?” Celestia asked, “I’m tired of all this Lulu, I have been for a while now and that incident with Tirek was just another nail in the metaphorical coffin.”

“But still sister, we feel as if there is something you’re not telling us.” Luna replied, “We thought we would have no secrets from each other. So please sister, tell us what is wrong.”

Celestia took a moment to think about her answer, and let out a small mischievous smirk. It had been so long since she had teased her younger sister.

“I would tell you Lulu, but before I do tell me how is my faithful student been? I understand that you two have been…studying late into the night, knowing what my dear Twilight is like when she was under my tutelage.” Celestia inquired, Luna gave her sister a raised brow at her sister’s question but answered anyway.

“Twilight Sparkle has been a wonderful pony to spend time with and teach, we see why you have such fondness for her, as she is such a joy to be around.” Luna answered.

“Ah yes.” Celestia smiled, “Those were good days, I would think I’m like a second mother to her but that aside I’ve heard you’ve been keeping her up late well into the hours of the early morning teaching her the rituals of the night.”

Luna froze in mid step in her pacing, and looked at her sister with a crimson blush adorning her adorable face.

“W-Whatever do you mean dear sister?” Luna stuttered trying to maintain her composure and hide her embarrassment. Celestia couldn’t help but smile at her sister’s futile attempts to hide her embarrassment.

“What’s wrong Lulu?” She teased, a knowing smile appearing on her graceful features. To the passers-by they would easily recognise the glint of mischief and playfulness in her eyes. “Why wouldn’t I have heard, after all I’ve been hearing it again and again every time Twilight comes to visit.”

“B-But…I-I…w-we…” Luna tried to come up with something to deny her older sister’s claims.

“You do know those silencing charms won’t work on that level of noise, and even then only another alicorn would be able to hear it.” Celestia explained, “Oh what was it again? Take us Twilight! Make us yours! Claim us! Fuck us harder Twilight!” Luna just stood there frozen in shock, the colour draining from her face as he blush intensified. “Am I right Lulu? I never would have thought you or my faithful student would be such naughty fillies or the fact my dearest little sister was such a screamer. I wonder if she has shown you that restraining spell yet, hm? Then again I did teach her well.” Celestia let out a quiet chuckle of amusement.

“Note to self: ask Twilight to show us that spell.” Luna mentally noted, “And what business is it of yours to ask about our private life?” Luna said in an attempt to defend herself.

“Oh it’s none of my business with what you do in private.” Celestia mused, “I just never realised…oh how did that useless nephew of mine put it…” She thought for a second. ”Ah that’s right, I just never realised that my dear sister was getting more pussy than I was.”

Luna stood there dumbfounded; she couldn’t believe her sister had just said that, she would never even consider her sister saying such a thing in a million years.

“Sister…I-I…” Luna tried to speak, but the words failed to form.

Celestia got up from her office chair, her expression unreadable.

“You know you’re so adorable Lulu.” Celestia spoke, a slender finger delicately on Luna’s chin bringing her eye to eye with each other. “It’s not hard to see why my faithful student is so enamoured with you.” Celestia drifted off for a moment.

“T-Tia?” Luna managed to squeak.

“I’m…frustrated Lulu” Celestia continued, “I’m very tempted to have a piece of that cake for myself, blood relations be damned. I’m positive Twilight would surely at least consider the idea of sharing you with me?”

“!?” Luna gasped, “S-surely you jest! R-right?”

“I’ve heard you Lulu; I’ve heard every single moan and gasp you make when she touches you, each flick of her tongue. I’ve heard it all Lulu and it gets me riled up every night!”

“B-but w-we belong to Twilight!” Luna finally spat out, “M-My mistress wouldn’t be happy with me!” Luna clasped her hands over her mouth. Celestia stopped for a moment and couldn’t help but laugh. Smiling she walked to her chair and sat back down clearly amused by Luna’s admission.

“Like I said my dear Lulu…” Celestia paused to pour a drink, “I taught my faithful student well.” She sipped her drink, “Now back to the matter at hand, I do believe being in charge of the day court would do you some good, and anyhow I thought you wanted to prove you could manage a bit more responsibility?”

“How can she go back to normal, after doing all that?” Luna wondered to herself. She was still trying to regain her composure. “F-fine, but what do you get out of all this?”

“Simple, a chance to relax and unwind without worrying you about all these damned politics and stuck up nobles demanding one thing or another.” Celestia explained matter-of-factly. “Besides I thought I would try my hand at a few things.”

Luna could finally see what her sister’s problem was, her role as a princess was making her a servant to the ponies of Equestria and it was taking its toll on her. Luna could see that Celestia wanted to be the one in control, to be the one dominating. It stuck Luna that she didn’t realise her sister had developed a side of her like that, but then again a thousand years can change anyone.

“F-Fine, we’ll do it!” Luna answered, before turning to leave, “We wish you a pleasant evening sister.”

“Oh and Lulu? Please be a dear and give my faithful students my regards.” Celestia chuckled as Luna remained silent as she left her sisters room.

“Because later you’re in for an eventful night.” Celestia thought to herself, “Courtesy of a favourite spell of mine, and I’m certain Twilight will appreciate it.”

Luna made her way to her quarters, hot and flustered after her encounter with her sister. She couldn’t help but wonder if her sister had meant all that, the thought of her sister doing everything Twilight did to her…

“Urgh…this is driving us up the wall!” Luna reprimanded herself, “I shouldn’t be getting so riled up about our own sister!”

Luna entered her room, the heat was beginning to get to her and since when did her clothes feel so tight. She locked the door, leaned on it and sighed, trying to clear those thoughts from her mind.

“Calm thyself Luna.” She told herself, “Tia wouldn’t do anything like that of the sort.” As much as she tried to fight it her thoughts couldn’t help but drift back to Celestia, and in an act of protest her hand found itself drifting along her silk gown, towards the wet heat between her long slender stocking clad legs.

“N-no…w-we won’t…” Luna tried to fight and dismiss those thoughts of her elder sister dominating her like her mistress Twilight did. “W-we refuse to get off to the thought of our sister…”

In the midst of her thoughts she didn’t notice every bit of her clothing becoming tighter, hugging every curve on her slender from.

“Oh no…Ngh! Oh nononono!” Luna became conscious of what she was doing to herself. “W-We will not submit to this! Damn it all when did these damned clothes become so tight?!”

Luna did her best to make her way over to her bed, futility trying to ignore the fires that had started in her now moist marehood. Flashes of her mistress lapping up the wetness of her lips with her skilful tongue, Lavender eyes staring hungrily at her, just daring to her to resist.

"My, why aren't you the naughty filly." The fantasy Twilight stated, a mischeivous smirk playing on her lips, "Is the thought of me and Celestia sharing you turning you on that much? Look at you, you're so fucking wet!" The fantasy Twilight laughed and resumed lapping up her lover's moist pussy. The thoughts continously playing through her mind, repeating itself as if it was a mantra.

“Ngh!...A-Ah-hah! M-Mistress..a-ah! Don’t stop p-please!” Luna moaned, finally giving in to her fantasy as she landed on her bed. Her hand was caressing her soaked pussy through white lace lingerie, as it seemed to tighten slightly with each touch and caress.

"Mmm, see was that so hard?" The dream Twilight asked in a seductive husky tone, "I don't mind sharing, I love the thought of your sister doing all those nasty things to you."

Luna found herself becoming more and more lost in her lust filled haze, rubbing her aching marehood harder than ever. Every one of her clothes becoming tighter with each lustful caress.

“This confounded dress! Ngh! Needs…to…go!” Luna said through gritted teeth, she grabbed the collar of her dress with one hand, and pulled tearing it open revealing her soft, full lingerie covered breasts straining their constraints as they seemed to swell with each caress and touch. The tingling sensation that now washed over her extended down to her hips and firm backside slowly expanding outwards.

“F-Fuck yes! M-more!” Luna screamed blissfully, “B-Bigger…Ngh! W-We want to be bigger! P-please Mistress make us bigger!” Luna practically begged the Twilight in her lust filled fantasy. "M-More! More!!"

Her lace lingerie panties soon showed signs of straining and tearing, and her breasts continued to swell larger and larger, increasing in sensitivity as they grew. Her bra was threatening to snap under the pressure of her expanding and swelling breasts.

Down the hall outside Luna’s room, Princess Twilight Sparkle walked her way down to see Luna the soft clicking of her heels. She took a moment to compose herself before knocking on the door.

“Luna?” She announced. “It’s me Twilight!” Twilight got no answer, she waited a moment before curiosity set in and she entered the room. As soon as Twilight and entered the room she was greeted by the sight of her…ahem not-so-secret lover pleasuring herself, begging and moaning her name as was lost in her own personal fantasy.

“Wait…is her breasts and ass getting bigger?” Twilight wondered, “Oh Twilight likes!” Twilight recognised the spell; it was a simple “Swell With Desire” she knew she didn’t cast it, and she knew fine well Luna didn’t either…

“What are you trying to do Celestia?” She muttered under her breath as she watched on, unnoticed by her lover.

Luna continued on with her performance, unaware she was being watched, her caresses becoming faster and harder.

“A-AH! F-FUCK!!!” Luna screamed in bliss. Her ass and hips grew and swelled wide enough that her panties finally gave way and her stockings torn with various holes throughout them due to her growth. Her breasts grew, swelled and expanded as they exploded out of her bra, as it finally gave way.

Twilight couldn’t help but stare on with awe, as Luna used both her hands to caress her massive, sensitive tits. Twilight suddenly had a kinky and naughty idea; she made her way over to Luna casting a subtle spell as she did so.

If Luna wanted to have some big tit fun, then Twilight was happy to oblige after all she was a fair mistress to her lover after all.

With each step forward Twilight’s breasts, hips and ass began to expand and swell to match Luna’s new found sizes, and in one deft motion Luna began to moan heavenly as Twilight got on her knees and began to lap up her lover’s juices.

“Ahn! Fuck Yes! Right there! D-deeper!” Luna moaned out.

“By the stars, she’s really into this.” Twilight thought to herself. She could feel herself becoming wetter, as her hips and ass expanded, tearing through those tight panties. Her breasts swelling larger, and larger straining her now tight blouse.

“O-oh fuck w-we want m-more!” Twilight cast the spell again answering Luna's plea, doubling the speed and size of both her and Luna’s growth. D’s soon became G’s, then L’s and continued onwards as they shredded through whatever clothing they had left, buttons popped, panties torn and in ruins on the ground, stockings ripped and full of holes, and her bra snapped apart unable to contain the sensitive massiveness of her breasts. Twilight buried herself deeper, not missing a single sweet spot on her lover's moist, aching marehood. She skillfully caressed, rubbed and thrusted roughly on her own aching heat with one hand, and rubbing, groping and playing with her wonderfully sensitive oversized tits with the other.

Each rub and caress of her breasts were making her wetter and hotter by the second, Twilight fucking loved the sight of Luna hungrily sucking her large puffy nipples, she was a total size queen and she knew it. She loved the thought of a big, busty and curvy mare beneath her, It was hard enough not to drool over and grope those monsters Fluttershy kept hidden underneath that sweater of hers and making her squirm was enough of a thought to keep Twilight awake and horny well into the early mornings. She didn't think her friends knew about this side of her, but you know what they say about the quiet ones.

Not satisfied with her own touch, Twilight conjured up a double ended dildo, and thrust it deep into Luna’s soaking tight wet pussy.

“OOOH! FUUUCK!!! M-Mistress?!” Luna screamed in utter bliss, her voice nearing the volume of the royal Canterlot voice. Luna looked at Twilight in utter glee, hungrily devouring her mistresses now curvy and busty body as Twilight slid the other end of the dildo into her own tight wet marehood. “Y-Yes Mistress! P-please fuck us! Fuck us hard! F-fuck us until we can't walk straight!”

“Gladly!” Twilight whispered huskily into Luna’s ear, “This is a reward for being such a naughty filly and treating your Mistress to a wonderful display."

True to her word, Twilight grinded and thrusted down hard on the dildo pushing the dildo further into Luna’s glistening wet marehood. A rhythm soon became a frenzy as she grinded harder and faster.

"N-ngh! I l-love this new look of yours I-I love how b-big you've gotten just for me! I f-fucking...N-N-ah! l-love big b-busty mares Luna!" Twilight moaned, "N-Ngh! Your tits look so j-juicy L-Luna I-I...O-oh stars! I-I could just suck them all day!"

Twilight began to grope and suckle on Luna’s enlarged, sensitive puffy cherry sized nipples making the moon goddess scream, moan and beg for more. Twilight made sure to grope with a firm grip on each of Luna’s enlarged breasts.

“M-Mistress…I-If you don’t s-top…w-we’ll!” Luna pleaded in between each blissful moan. This however only encouraged Twilight to grope and suck harder, and with a not a moment later…

“A-AHNNNN! T-Twilight!” Twilight happily continued sucking and swallowed up her lovers milk as it gushed into her mouth and down her throat, further driving Luna into a frenzy as she felt her hips bucking and grinding against Twilight’s hips.

"You know what, fuck it!" Twilight thought to herself, and clicked her fingers three times. Luna and Twilight's expansion continued, their breasts, hips and asses swelling larger and larger once again. With each suck Twilight could feel Luna's breasts grow more and more, as she continued to hungrily drink her lover's milk, guzzling it down with out a single care.

As she drank Twilight could feel her belly swell up little by little and soon Luna began to suckle on Twilight's expanding tits. Twilight moaned in bliss as Luna sucked and groped her massive sensitive breasts, she knew that Luna wanted in on the fun, fully intent on milking her.

Soon Luna's belly began to swell up like Twilight's, each little bit of growth driving them further and further into orgasmic bliss, making both them look like two curvy, huge assed, monster titted goddesses indulging in hot, kinky lesbian sex. The thought of it alone was enough to getting Twilight off. Their bellies continued to swell further as they guzzled down each others milk, making them look like they were heavily pregnant.

With another snap of her fingers, the double ended dildo began vibrate furiously, and began to thicken and grow inch by inch slow stretching the walls of their pussies, and filling them both up. Each vibration quickened the pace of each grind further, they both sucked harder each others monster sized tits, until the it was too much to swallow and drenched them both in each others breast milk.

They both moaned, groaned, and screamed louder and louder, their orgasms were building up, coming closer and closer as their volume increased be loud enough to rival the royal canterlot voice, neither cared if they screamed all of Equestria awake with their climax.

The pace was quickening and between them and soon Twilight was joining Luna's level of noise in her screams and moans of orgasmic bliss.

“I-I’m g-gonna! I-I’m g-gonna! NGHHHAHHHHHHHHH!!!!!!!!” Both screamed in bliss. the entire room shaking from the sheer volume. Thankfully both Luna and Twilight had long sinced magically reinforced the room to prevent any damage to the castle. Exhausted they both collapsed, left tired and drained, they panted heavily trying to get their breath back.

“F-fuck Luna, if I knew you were into growth and expansion, I would have done this sooner.” Twilight said, in between pants. Twilight looked around the room to see it was in complete chaos, a good portion the room was a complete mess with books, quills and ink, torn and shredded remnants of their clothing on the floor, not to mention they and the bed were both drenched from their milk, sweat and juices. Here they both were huge breasts, hips, asses and bellys, hot and sweaty. They were truely a picture of many a stallion's fantasy.

“O-Oh shush you!” Luna replied with a satisfied grin on her face, “How long does this last anyway?” She asked pointing to her double V-cup sized breasts, 60 inch ass and hips, and her now swollen milk filled belly.

“T-That’ll wear...off in two...to three hours.” Twilight answered in between breaths, “Let me guess...Celestia?” Luna nodded, breathing heavily her enlarged breasts giving a subtle bounce with each breath.

“I take it...s-she knows...about us then?” Again Luna nodded, “Well I’ll be sure to consider whatever proposal she has in mind.” Luna just stared as Twilight in utter disbelief. "F-fuck I have got to convince Rarity and Fluttershy to join us sometime."

“Remind us...to thank and kill...our sister later.” Luna stated, ignoring her lovers remark.

“Hmm, well I don’t think you’ll get the chance to any time soon.” Twilight said in a very amused and seductive tone fnally getting her breath back, Twilight groped Luna’s breasts in a firm grip and whispered into her ear, “I’m far from done with you yet.” Twilight let out a low chuckle as she groped Luna’s breasts to emphasize her point.

In another part of the castle, Celestia could hear blissful moans and screams coming from Luna’s bedroom. Putting the ink quill down, and smirking to herself.

“I see Twilight and Luna are enjoying my…incentive.” Celestia couldn’t help but laugh. “Ah well I’ll finish this paper work up for the evening, and maybe have a little fun myself.”

Omake: -

In the Crystal Kingdom, The Princess of Love Cadenza Mi Amore or Cadance for short was working in preparation for the upcoming celebration alongside her husband Shining Armour. She couldn’t help but catch something on the echo of the wind off to the distance.

“What’s wrong honey?” Shining Armour asked concerned. Cadance just smiled and giggled in amusement.

“Oh it’s nothing bad sweetie, just the sound of the apple not falling far from the tree.” Cadance answered amused.

“Huh?” He replied dumbfounded. “Ah right whatever you say honey.” He continued not quite understanding what she meant.

“I think you’ll find out next time we visit Canterlot.” Cadance continued. “But I’m not saying a word until then. Besides you’re gonna have your work cut out for tonight. I would hate for you to be out done by family.”

Shining didn’t quite get it, and shrugged who was he to argue.

Author's Note

Just in case you wanted the notes for that spell used in this chapter for your own story.

"Swelling With Desire"
A spell cast typically cast by touch, although a skillful caster can cast just by eye contact or snap of the fingers. it increases the perportions and sensitivity of whatever the user desires to grow and expand. It can be cast on one target mutliple times, each time doubling the speed, size and pleasure of the growth with each following cast.

It's been a while since I wrote a scene like this, so tell me what you think in the comments.

Enjoy and Stay Classy
-Silent

Edit: fixed abit of the grammar and extended the chapter abit.
Edit 2: Another grammar fix, and slight extention of the chapter. Fuck if you're going to write a lesbian breast and ass expansion scene you might as well do belly expansion too. Don't get me wrong this is going to try and atleast be a somewhat serious story, but lets face it if your going to write smut you go all out with it....