With the reaction to the adulthood question mixed with the flower theory, it's entirely possible these children die very young. I will not go as far as saying they do so shortly after their first sexual intercourse... But who knows what in the head of the author before we get there ?

I like the clone theory too. They globally know what are the attibutes of lines of clones, although they probably are altered every generation.

As for that poor Zero2 pilot we saw, I think I remember them saying pilots grow older insanely fast with Zero2 in Strelizia