I'm interested in how you expect someone to attend school/retrain without childcare. You can't generally bring your kids to class with you.
And I suspect disaster to have correlated chances of killing parents or grandparents or children. i.e. if you've become a parent there's a good chance your parents did too.
Our own lived experiences are likely outliers, since developed countries have different outcomes than the past.
Crap and nonsense! Rewrite:
Once someone's survived to become a parent, there's a good chance the grandparents survived as well (assuming the norm is to breed ASAP).
However, most people in America can't rely on grandparents for childcare. One reason is we have children much older than people in the third world do - if two generations have children at age 38, it's not very reasonable to be expecting a 76 year old to provide child care.