Boys don't matter that much here. The fertility limiter in humans is female fertility. Male fertility is basically ~13 years old to around 60-80 depending on individual and ethnic group.
For females, this window is much narrower, and optimal window is very narrow. Optimal starts around 14-16 (depending on ethnic group) and it crashes into geriatric pregnancy between late 20s and early 30s and sterility between mid 30s to early 40s (again depending on ethnic group).
The really fucked up part no one is talking about? Blacks just crashed way below pretty much everyone else. Their fertility window is earlier than the rest, their optimal is something like 14-25, and they slide into geriatric pregnancy around 30 (for europeans and asians, that's usually around 35). So when rich white women finally got the "don't have kids early, have them only after you have full education and career" fertility suppression strategy affect blacks, their ethnic group's fertility crashed much harder than the rest. The sheer amount of "DEI boss babe" black woman types being genuinely distressed that they're in their early 30s and they find out that they're actually so far into their geriatric pregnancy stage that they have low single digit percentage to get pregnant even with modern IVF is staggering, and their ethnic fertility rate is showing it.
Seriously, look up a few of those videos on tiktok. It's genuinely distressing to watch if you have any empathy. These women really want children, they have been told by rich white women that they should put it off as a part of female intersexual competition (human females' primary intersexual competition mechanism is suppressing fertility of other women). And whereas their european and asian colleagues can actually start having kids in early 30s with only minor difficulties, africans are basically off the cliff into geriatric pregnancy/borderline sterility at that point. So system told them their whole lives that if they do this, they'll have the dream family. They structure their whole lives around this lie, and then the dream is shattered when for the first time in their lives, MD tells them the actual truth about their biological limits.
It's heart breaking stuff.