Never really thought about this, but I'd read it. Anypony else?

I don't even...

1313313
I'd say yes, but I'm not a pony, so I don't count

Considering Rarity's talent, it makes sense. The story would require some tweaking, but it could work: Assuming Sombra only returned to the public after he recuperated a large part of his power (or after he heard the crystal empire is back) we would have had time to concieve Rarity - who either grew up with adoptive parents (ala Harry Potter - only in Sombra's case he had to maintain the illusion that he was dead) or has in fact lived far longer and regularly transforms into a filly to hide with new families (they simply find her in a basket at the doorstep) - the story of her cutie mark is true but the magical burst that broke open the rock was from Nightmare Moon's banishment a thousand years ago.

1315691 Dude, its not Rarity, but Princess Platinum.

And that story exists, its called Unexpected Life of Dusk Shine. Spoilers: thats kinda canon in that story.