I think having two children replace us on the already overcrowded planet.
I judge large families by the size of transport required to ferry them about.
Not everyone has a car, but assuming you have one, when you get to three children that means having to buy a ‘bigger’ car which is large enough to fit all the huge car seats, and four or more children need an even bigger people carrier type car. So four or more is definitely large to me.
We don’t live in Victorian times when there was no reliable birth control, when so many children were born and many died.
It’s a rare tragedy that we lose our babies /small children now, we assume they will live to adulthood and beyond, and most do, but admit I secretly hankered for a third child, but we stopped at two and had a regular small car.