The Wold Newton family is a literary conceit derived from a form of crossover fiction developed by the science fiction writer Philip Jose Farmer. Farmer suggested in two fictional "biographies" of fictional characters (Tarzan Alive and Doc Savage: His Apocalyptic Life), that a radioactive meteorite fell in Wold Newton, England, in the late 18th century, resulting in genetic mutations affecting the occupants of a passing coach. The progeny of these travellers were purported to have been the real-life originals of the semi-fictionalised characters, both heroic and villainous, in fiction over the last few hundred years, such as Sherlock Holmes, Tarzan, Doc Savage, and Lord Peter Wimsey.
An earlier proponent of this sort of fiction was William S. Baring-Gould who wrote a fictional biography of Sherlock Holmes. In 1971 C. W. Scott-Giles, an expert in heraldry, published a history of Lord Peter Wimsey's family, going back to 1066 (but describing the loss of the family tree going back to Adam); the book is based on material from his correspondence with Dorothy L. Sayers, who wrote at least two of the family anecdotes in the book, one of them in medieval French.
A similar premise has subsequently been adopted by Alan Moore in his comic book series The League of Extraordinary Gentlemen. Warren Ellis's comic book series Planetary has a similar premise of fitting many different superhero, science fiction, and fantasy elements into the same universe.
The Wold Newton concept relies on judicious Krypto-Revisionism; the characters of the books and comics are treated as fictionalized, exaggerated versions of "real" people/characters, and accounts that strain suspension of disbelief too much are dismissed as complete fabrication.