In my experience, this is more of a social issue not tied to economics. Consider certain subcultures (religious Jews in the US, for example), where having lots of kids the social norm, without any obvious economic reason.
Personally, most of my childhood I was a single child (and not too social), and I think having a big family would have been a lot more fun.
Personally, most of my childhood I was a single child (and not too social), and I think having a big family would have been a lot more fun.