So, in this AU Sombra doesn’t attack the crystal empire and second time (I’ll have another post about that whole situation!) But the main thing is Sombra feels super aimless and is trying to fit-in in modern day Equestria.
And who better to teach him about modern day Equestria than Mr.Popular himself! Fancy grew up in a very broken home and knows what it’s like to be in a dark place, that’s exactly why Rarity recommended to two stay close to one another.
Closer they did get, with much distaste from Fleur (she thought Sombra was pretty suspicious but he’ll grow on her.) the two got together after Sombra’s whole redemption arc. They have two kids named Radiant Hope and Cimmerian.
this is definitely the more headcannon and crackship part of this next gen but I hope you enjoy!