In unindustrialized agriculture having a lot of children is a sound strategy. The first couple years they cost you food and time, but after that they are cheape

In unindustrialized agriculture having a lot of children is a sound strategy. The first couple years they cost you food and time, but after that they are cheaper than employing workers, and they will even take care of you when you are too old to work the fields. And without modern healthcare a lot of them will die. If you want to make sure one of them inherits the farm (and provides for you if you manage to become old) you need to have enough children to achieve this at an acceptable level of risk.