I agree with this for the most part, however it was mentioned in passing that it's a very big coincidence all 5 founding families have sons/daughters in the same year at the same place. Considering one of the families was considered lost the coincidence is even bigger. Perhaps there's a bigger plan going on in the background.I think it's safe to assume that there's more sons from the families who are older, younger or from branch families that are less relevant to the immediate politics. MC's perspective on the main families is mostly limited to around his age range.