There's a fairly simple answer to this question

Over in The Guardian there's a question asked that rather horrifies us:

What is the correct number of children each of us should have? It’s a question to which we urgently need an answer – made all the more necessary by the latest reported figures, which show that Britain now has more families with four or more children than at any time since the 1970s. According to the European statistics agency, Eurostat, there’s a growing trend for large families – even though the average family size is getting smaller.

Should this be celebrated, or condemned? We need some guidance, surely. If not, how are today’s young people of childbearing age ever going to work out what to do?

The horror coming from the fact that if there is some "right" number of children that each couple, or woman, should have, then obviously there has to be someone, somewhere, who decides what that number is. And then, naturally, some system of enforcement. And when there's enforcement of anything like this we get to the horrors of those Chinese and or Indian systems of forced sterilisations, enforced abortions and the rest. Things that have also happened, on a smaller scale, here in Europe within living memory.

Thus the correct answer to the "how many children should people have?" question is: none of your damn business matey.