In this context, I assume a "large family" is 3 or 4 children (a 5 seat sedan cannot physically, legally fit 4 children and two parents, and due to the size of

In this context, I assume a "large family" is 3 or 4 children (a 5 seat sedan cannot physically, legally fit 4 children and two parents, and due to the size of modern carseats it can be dicey or impossible to fit 3 of them in compact or midsize sedans even for a 3-child family). Even just maintaining replacement rate fertility requires an average of 2.1 children TFR, which means some families would need to have 3 or 4 children to get there since other families will have only 2 or 1 child.