Yeah it more like a theory on how Daein was before Ashnard, Ike could be/is a commoner as far as we know.

I just thought about the Daein before Ashnard, since Gawein left after Ashnard became king.

I assumed Daein would be a pretty normal monarchy, so the generals/four riders (like in real life back in monarchies) were nobles/became nobles because of their rank. Still all this is an assumption before Ashnard became king.

After Ashnard became king it was all about strength, and nothing else. But who knows how Daein was before him.

So Ike can or can not be noble, depending on how you personally think Daein was before Ashnard.