I still think it's a really weak definition if you give out arbitrary date ranges which inevitably leads to random smaller generational definitions and too many varying opinions on what generation starts or ends where.

The point of generational cohorts like millennials or the silent generation is that being born at a particular time in history has an affect on people.

The silent generation's earliest memories were depression and war. The great recession impacted millennials in their early career or in high school.

Age ranges captures that and makes it easy to measure things without having to find out when someone's great grandparents were born.

And yeah, 30's on the young side. Lauren Boebert was in the news recently as a teen mother who became a grandmother at age 36.

Your definition slips pretty quickly, though. Some siblings have really long age gaps. Some women first give birth at 18 or 19, others not til they're 40.