In uk.rec.gardening Lewis wrote:
In researching the family tree a couple of decade ago I came across one
ancestor who had 3 wives, all three died in childbrith, and in total
they had 21 children. *TWO* of those children lived to adulthood.
Granted, those numbers are a bit extreme.

I would be inclined to suspect some kind of genetic problem going on
there. Was there any gender split between survivors and non-survivors?