From the description:
 
“Silverbones is the third eldest of Sweetie and Silver’s nextgen brood. Of their five children he is the only boy, the only adoptive child and–oh hey!–the only non-pony.
 
A griffon egg abandoned within Equestria’s borders resulted in a dead end as the authorities searched for its origins. Unwilling to allow a sentient baby to be hatched and raised the animal sanctuary, Fluttershy insisted that the little lost egg be given a real home with a pony family, or shipped back to Griffonstone to be with its own kind (ideally the former; griffon orphanages aren’t known for their tender loving care nor uplifting musical numbers). Enter Silver Spoon and Sweetie Belle, who’d been hoping to have another kid anyway (though Bee insists it was all her idea) and who certainly possessed the funds to properly care for a (very) special needs foal. Hatched at Silver Manor, the little griffon chick was instantly embraced and loved by the whole fam damnly.
 
Silverbones may not be the prettiest griffon you folks can imagine, but his indefatigable intellect and gentle heart contradict his unsettling appearance. His quiet wisdom and intelligence allow him to eventually accept the reigns of the family business from his grandmother. Meanwhile, his mothers, aunts and sisters have an irresistible tendency to fuss over and coddle him, because he’s so lovable and uglycute (except Chase, of course; she doesn’t coddle nopony no-how).
 
mlp:fim = Hasbro/Faust
 
Post-script: Naturally lacking a cutie mark (unlike one of his moms, who unnaturally lacks a cutie mark),
 
Silverbones had the Silver family crest tattooed on one of his forelimbs. I’m told that very soon there’s going to be a canon episode in which the CMC council a griffon kid who’s fretting about its own absence of a cutie mark (because, y’know, it’s a fucking griffon). Anyway, no relation.”