Personally, since Celestia and Luna are god-monarchs, I prefer the idea of alicorns being 'born' from magic (a critical element of the Equestrian universe) rather than being conventionally and organically conceived. Meritocratic reproduction, rather than biological reproduction. (Though, now it would seem that both origins are possible.)
I used to take the show seriously. Not so much anymore, especially since I can slap a big ol' "I started this before S2 started" sign on BWSD and disregard canon that might clash with my fanon.