
You do not have to have the wir title to be nobility. It simply denotes relation to the imperial family. Nael van Darnus was from a long and prestigious noble family, but was not related to the imperial family. Similarly Cid Garlond is also from a prestigious/noble family, and is not related to the emperor. Nero is from a rival family to Cid's, so it can be assumed that there are noble houses past the imperial family. I think House Darnus is actually mentioned by name somewhere too.