[If their world was anything like how it was a hundred years ago, it's unlikely. When most of your children can be expected to die off before puberty, there's no other chances to learn.]

It becomes progressively harder to learn how to mold and increase your chakra reserves the older you get. Since chakra is the combination of physical and mental energies, the single best time to go about this is as a child, when you're still rapidly developing. It's the time in which we learn the most, and our bodies are also at their most adaptable.

[He raises a finger.] It's not impossible to teach someone who's older, but it will take more time to achieve the same results, with added difficulty for the student. I've noticed this, in training Masaomi.