Mr & Mrs. Ultra Prole (if they're even married, usually not) have kids as teenagers or 20 or so bc they don't have any real life plans and are too dumb/ratchet to use contraception and want to start collecting benefits.

Middling proles have kids a bit later, like 23-25. They're simple folk. When mechanic Johnny meets Cosmetologist Lydia, they just hitched and started popping them out.

UMC to elite tend to have kids later due to educational and career restraints, having to go to school longer and focus more on career, so it's typically kids in the 31-36 range.

Some of the most elite want to cram in more life experience and so wait until almost 40.

(http://www.autoadmit.com/thread.php?thread_id=3897288&forum_id=2#35435372)