Nadieh Breme's Royal Constellations is a delightful starry visualization of a millenium of familial connections between European royals, and it gets right down to business: "Royal & aristocratic families are known for their fondness of marrying within their own clique."
Pick any two and it draws a line between them, revealing ancestral lines going back to the beginning—from the kings of medieval Wales all the way to the Windsors.
