Board Thread:Theories and Speculation/@comment-30415965-20171104121848/@comment-734582-20171105112013

BlazeRelease wrote: I think, he's asking about why all the Konoha ninjas of the past generation had kids at the same time. It's often the case that people among a friend group get kids at roughly the same time (just a few years apart), because they hit the age where they both start thinking about kids and can financially support them at roughly the same time.

It's also important to note that Naruto only follows a handful of people in a world of hundreds of thousands of ninja. So it's also the mother of all sample biases.