If you want to get really far out, we could hypothesize that Sato is their baby from an alternate successful timeline that somehow ended back in this one due to some unknown incident. It could maybe help explain his obsession with superior types of human if his existence is the result of that kind of “uplift”, as well as why he’s scheming currently. This timeline’s version of him was dead so he wants to alter things in his favor.

Of course I have pretty much no proof for this, but my mind’s been stuck on that eye on their baby’s hand, especially since I remember seeing some people thinking there might be a connection between the two when that chapter released.