Comment by chrismorgan

If I’m reading you correctly, you seem to think that two kids takes twice as much effort as one kid? People broadly agree that cost and effort both grow sublinearly. Especially effort, though it is of course much harder to quantify. But personally I suspect that even four kids (serially) may not cross the twice-as-much-effort threshold. Aging affects the amounts and types of effort required, too. Four kids in parallel (quadruplets) will definitely be more than twice as much effort for quite some time!