William Cecil Clayton was undoubtedly one of the most prominent members of the Clayton Family, with the obvious exceptions of his uncle and nephew. The younger son of Sir Jesse Clayton, 4th Duke of Greystoke, William Cecil went into politics, successfully standing for election as Member of Parliament for Chester. He served as Lord of the Admiralty, Vice-President of the Board of Trade, Lord Privy Seal, and Chief Secretary of State for European Affairs.
Lord William Cecil Clayton, as he was then known, was unmarried, as the love of his life Patricia Clarke Wildman had refused his proposal of marriage because she feared that the scandal surrounding her father's death would damage his career. She died following the birth of their illegitimate son, James Clarke Wildman, for whose upbringing Lord William Cecil took responsibility, although the relationship between the two remained a secret.
In 1885, he purchased a stately home, Pemberley, from his cousin Sir Gawain Darcy. He also attempted to have his eccentric elder brother, the Socialist John Clayton, 5th Duke of Greystoke certified as a lunatic, after the Duke was prosecuted for taking part in a riot connected to a dockers' strike.
In 1887, Lord William Cecil Clayton was raised to the peerage in his own right as Marquess of Exminster and Viscount Passmore; he was also created a baronet. The following year, he married his elder brother's sister-in-law, the widow of Lord Blackwater, in a double-ceremony that also saw the Duke's eldest son Lord Staveley married. In 1889 the fifth Duke was murdered and, with his son's family missing and presumed dead in Africa, Lord Exminster succeeded as sixth Duke.
In 1891 the Duke and Duchess celebrated the birth of a son, William Cecil Arthur, who would go on to succeed his father on the latter's death in 1909. In 1901, the boy was kidnapped by his father's secretary "James Wilder", whom Sherlock Holmes unmasked as the Duke's illegitimate son. These events were chronicled in "The Adventure of the Priory School", and it was his feelings of guilt at what transpired as a result of the kidnapping that prompted James Clarke Wildman to push his infant son - later, Doc Savage - into a life as a crimefighter. The Duke paid off the detective to allow his son to escape justice.
The above information is predominantly drawn from Tarzan Alive by Philip José Farmer, the precise relationships of the various Greystokes being a modification of Professor Starr's theories. Arthur C. Sippo's article "Further Thoughts on the Doc Savage Chronology" links the sixth Duke and James Clarke Wildman to the protagonists of the novel The Lost Ones by Ian Cameron, perhaps more familiar through the (more accurate, per Mr. Sippo) movie adaptation The Island at the Top of the World. Matthew Baugh's article "Sailor Steve and the Iron Men" argues that a detective named Sir Cecil Clayton encountered by Sailor Steve Costigan was a younger son of the sixth Duke.