For what I understand both his parents are omega and michi is an omega too. That's why his father didn't realise that Hiro is Masaki's husband, cause he's assuming that he was married to an omega (just like him and his wife were both omegas, maybe he think that omegas can live happy only with other omegas)...
That's what I understand, maybe I'm wrong
Don't know, I read omegaverse "rules" once but I don't really remember. I think omega male x omega male is not possible, but if it's male x female it's probably okay... but why, what's the difference between this two options ?
Also I guess the rules depend on each author, everyone make his own type of story ^^
so most likely michi's mom is an beta??? perhaps??? seems like daddy doesn't involve himself with alphas?