[EDIT for clarity:] The boomers are a populous generation, and their children the millennials are also populous in a sort of "echo". It makes sense, that lots of parents would have had lots of kids. X are a less populous generation sandwiched in between those other two.

https://nerej.com/generation-y-also-known-as-millennial-or-e...

Boomers somehow gave birth to two generations- you had some still getting married and having kids right out of high school (kids would be Gen X) but you also had the 'Me Generation'/Studio 54/Gordon Gecko half who put off kids for career/lifestyle or spread them out over multiple marriages. I have a coworker who is 22 years younger than me despite our parents' ages being about two years apart. He's barely a millennial, while my childhood was pretty much as documented in 'Stranger Things'.

Gen-X aren't the boomer echo, they're the boomer bust.

Sort of the negative space propagating up the demographic pyramid that slacked breifly and was never heard from again.