I don’t even believe all these connections. It’s just too convenient, that all these famous people are related to each other. Surrrre they are. not.
Actually, it's not surprising at all. The secret is that everybody is related to everybody. You go back ten generations and you have 2046 direct ancestors. Factor in siblings -- probably many thousands more, and their children -- and in just ten generations you'll find you're directly related to hundreds of thousands if not millions of people.
That’s why geneology is bullcrap — because you’re almost certainly descended in part from kings and princes and whatnot, just as everybody else is. I read something once that something like 80% of all people of European descent had Mohammed as one of their ancestors — the math is incredible, but after you go back far enough it becomes totally meaningless.
Why? Going back 10 generations (~250 years) you have 1024 (210) ancestors. Going back 20 generations (~500 years), you have 1,048,576 (220) ancestors. Going back 30 generations (~750 years), you have 1,073,741,824 (230) ancestors.