Here, then, extremely belatedly, is the promised second footnote to the Last And First Men book review. This one is about Olaf Stapledon himself, rather than some inconsequential bollocks about imaginary faces on book covers.
As you can discover easily enough on Wikipedia, Olaf Stapledon was the son of William Clibbet Stapledon and Emmeline Miller. You'll have to trust me on the rest, though - here we go: William Clibbet Stapledon was the son of Elizabeth Clibbet and William Stapledon, and Elizabeth Clibbet was the daughter of William Clibbet, who in turn was the son of persons unknown (but who presumably went by the names Mr. & Mrs. Clibbet). So, if you're keeping up, you'll have already worked out that this Mr. X. Clibbet was Olaf Stapledon's great-great-grandfather.
Here's the good bit, though: this mystery Clibbet was also my great-great-great-great-grandfather. He also had a daughter called Susan Clibbet, who had a daughter called Blanche, who in turn had a daughter also called Blanche, who had a daughter called Edith, who had a daughter called Susan, who is my mother!
So Olaf Stapledon and I are distant cousins. Working out the exact relationship in this sort of situation gives some people a migraine, but it's actually fairly straightforward once you know the rules - the Wikipedia page explains it pretty well, and also has a cheeky chart if you can't be bothered to work it out yourself, or just want to check your results once you have. You'll be able to use the chart to verify that Olaf Stapledon and I are third cousins twice removed. Here's a sketched family tree (relevant parts only):