Wrote this on Anon in the incest thread a few months ago.
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>>You will never have to rule Equestria because parents are dead. A teen Celestia scaring off potential suitors and conniving nobles trying to get ahead, figuring since you are king, then she should be queen With all that entails A few years later Luna is born

>>"I'm sorry! P-Please, I was just looking!"
>A maid rips past you, running as quickly as her two legs and frilly dress will allow.
>Behind her, kicking her two-thousand-bit Royal Heels off of her feet, pursues Celestia.
>Your sister is running like the demons of Tartarus are behind her... but the fire in her eyes and the claw-like way she reaches out for the maid with her manicured fingernails makes you think that the demons are alive and well in Celestia, and it's the MAID that's running from them.
>"Get back here, you skank! I saw what you were doing with my brother's underwear! I SAW!
>Just as Celestia passes you, you lunge forward and grab her around the waist.
>She squawks in surprise as you spin her around to bleed off her momentum, and the dizziness that follows means that the two of you collapse into a very angry, very disorientated pile.
>"Let me go!" she hisses, struggling against your grasp, "Let me teach that fucking WHORE a lesson!"
"Celestia! Celly!" you yell back, squeezing her around the middle and trying to avoid getting head-butted, "It's ME, you fuckin' loon! Settle thee DOWN!"
>Your little sister struggles for new a few moments longer before going limp in your arms, like a fussy toddler who doesn't want to put her winter outfit on.
>"A-Anon..."
>Celestia's quiet whimpers pitter away into gentle sobs, and her struggles slowly give way to shaking shoulders.
>"Th-those fucking maids..." she croaks, voice quivering, "They n-never would have t-tried to perv on the k-king if mom and d-dad were still around..."
>You flip your sister around so that she's facing you and then wrap your arms around her, pulling her into a tight hug.
"Oh, Celly..."
>"The wh-whole world's falling apart, Anon!"
"Shh..."
>You sit there for a long time; sister in your lap and tears slowly dampening your shirt.
>"I m-miss them so much..."
>You kiss the top of Celestia's head and hum comfortingly, like how mom used to do when you were younger.
"I know, my little loon."
>Celestia whimpers and rubs her face against your chest.
>'Loon' was your father's nickname for her, since your sister is a little bit... "eccentric".
>Chasing a maid down the hallway for the treasonous crime of cleaning your dirty laundry should be a testament to this.
>You're a few years older than your sister is, and so you're taking the deaths of your parents a little bit better than Celestia.
>Not much better, but enough that you can hold yourself together long enough to comfort your little sister.
>You aren't sure how much time has passed before Celestia speaks again.
>"Anon? I have a confession to make"
>You remove your cheek from the top of her head, and Celestia lifts her own noggin from your chest.
>"That... that wasn't a maid."
>She has trouble meeting your eye.
>"That was a suitor."
>...
>Huh.
"You know," you drawl, "I THOUGHT that maid was dressed up especially slutty..."
>Celestia giggles, and you mentally give yourself a "good big brother" point for taking making her laugh so soon after she was crying over your parents.
>[spoiler]You're up to 30 points.[/spoiler]
>"It's just... not fair."
>Your little sister rests her head against your chest again.
>"It's just you and me now, Anon," she says, her words muffled slightly by your ribcage, "I don't wanna lose you..."
>You give her a little squeeze.
"You won't," you say plainly, as though such a sentiment was obvious, "I promise you'll always have me, you loon."
>Celestia suddenly looks up at you with determination on her face and a fire in her eyes.
>Before you know it, her lips are mashed against yours.
---
>You are Anon, and it is the next morning.
>You are lying awake in bed, absolutely naked under the sheets.
>Your sister, equally naked, is draped over your chest, fast asleep.
>You can feel the cum leaking out of her pussy and making a messy stain on your thigh.
>You're pretty sure you just lost all your "good big brother" points, and are easily in the minuses.
>Is it possible to be shell-shocked despite having never fought in a war?
>...
>Welp.
>You're pretty sure you just made your princess sister into a queen.
---
>As the months would go by, you'd find out that your little sister was especially fond of the nickname "loon", and decided to name your daughter after it as a gesture of how much she loved her.
>"Luna" it is, you guess.