JOE is ranked as the 103rd most popular given name in the United States with an estimated population of 580,202.There are 181.96 people named JOE for every 100,000 Americans. World, who knows? That's irrelevant though.
I suspect there are very few people with the only unique first and last name in a planet with 8+ billion of living people on it, never mind dead. Probably many thousands of most peoples same name combination, especially the more common first and last ones.
There's probably a variable but non-exact formulae depending on how popular the names are, e.g. here - https://stats.stackexchange.com/questions/151579/probability-match-of-first-and-last-name-in-group-of-n-persons