What a lot of conservative men have massive cluelessness about is how having babies impacts women and can actually inhibit fertility multigenerationally. Ok, so you wanna outbreed those dastardly liberals. The way to do that is not by having wives produce a dozen kids. They aren’t really cheaper by the dozen.
Once you’re in double digits for sure and generally speaking at some point after about 6-7 kids, a large family inhibits fertility. With that many kids, there’s free riding (“Oh, some of my numerous siblings will provide grandkids, no worry, no hurry”), and there’s childcare burnout because as the Duggars usefully show, there’s no way Mom can be pregnant near-constantly and also take care of all the kids. It generally falls to older female siblings once they are aged 9-10 or so, who unsurprisingly tend to be disinclined to rush into motherhood, or even pursue it at all.
There’s also the two or three family problem, where because of the inevitable wide gaps that open up between the oldest and the youngest, you just might get the household segmenting itself into little sub-units where some of the siblings take on mother/father roles because they are 15 years older than the littlest kids. That also inhibits fertility, by simulating the parent/child relationship in what is not necessarily a healthy way and which delays family formation.
The takeaway is that you can look with your eyes at the generational spread with such families. Parents have 12 kids, who typically have 15-30 grandkids between them, a huge drop in fertility. And since those grandkids grew up in families much much smaller than what their parents had, that inhibits their own baby-having even though they know they have a zillion aunts and uncles. At the low end of that range, several of the 12 didn’t even reproduce, further dinging the overall robustness of the family tree.
That’s how it tends to play out in reality-land, as opposed to daydreamland when conservative men propose that the solution to have normal life return is just for conservative families to pop em out like pez.
If one is really set on robust reproduction, the approach that gets you multiple generations of 3+ kids per mother is to arrange your society so that people expect to see 4-6 kids as a “typical family”. Some families will be smaller and a few will be much larger, but that range of kids is manageable. If the couple wants to “get it out of the way” and have them closely spaced, that’s an option. If they want to follow a more natural spacing and rest up between each kid, that’s an option. It’s not so many kids that daughters grow up seeing a constantly tired, constantly pregnant woman who keeps giving them more and more work to do. It’s not so many kids that sons are really worried about how on earth they could possibly support so many babies.
But it’s not so few kids that people stop getting used to seeing children in the public sphere. It’s not so few kids that helicopter parenting is high-status, nor so many kids that nobody expects much in the way of fathering or mothering to happen.
And in practice the result is that parents have 4-5 kids who have 4-5 kids, who…have 4-5 kids. The occasional kid doesn’t reproduce for whatever reasons, but overall 3 or 4 of every five do, and typically by having about as many as their parents did. This is much more robust and builds a strong community of kinship and openness to children as part of normal life in general. The divides between parents and non-parents don’t have the same kind of space to open up and make it difficult to keep kids in the public sphere.
Yes, this is a Mormon approach, and where they’ve bought fully into the birth control mentality, it’s stopped working. But it’s also the approach for a lot of societies, including a fair amount of America during the early and middle 20th century when America was more regional.
Caveat: this post assumes that when (male) people promote having quite a bit more than two kids that they are sincerely clueless about how exhausting the raising and bearing of kids is and that they would welcome a society where motherhood was taken seriously and supported as a vocation and real lifework. It is not a post that assumes these people actually want the way worse than purdah system their blithe advocacy ends up producing in practice. It assumes good intentions, which may well be overly generous on my part, but there you are.