I guess the birth date of people on Wikipedia normalized in order to be indexable?

I have a (stupid) theory that I would like to test but I don't know how to go about it. The theory is that many (most) people who go on to achieve great things are orphaned (or estranged) from their father at a young age (before they're 6).

A first step to test it would be to calculate the correlation between the age of the person when their father died, and some measure of their "greatness" (length of article? number of sources?)

But I don't think the information about the year of death of each parent is normalized; any idea in how to go about this?