This is a phenomenon (harsh in the case of Jiro's son amid modern sensibilities about free will and obligation), which is said to have fueled some aspects of human exploration (and also unfortunately the bad aspects of it) in history.

The 2nd son didn't inherit under the doctrine of primogeniture, leading the later sons to be the (often) neglected or less favored / wealthy, motivating them (for better and worse) to set out on their own and prove their worth.