Edith Jansenius was the daughter of Sir John Jansenius and Ruth Rothschild. She married the Marquess of Blackwater, who predeceased her, and then in 1888 the Marquess of Exminister who later became Duke of Greystoke; their son was William Cecil Arthur Clayton, 7th Duke of Greystoke. She was also the original of the "wronged woman" who shot a notorious society blackmailer in the Sherlock Holmes story "The Adventure of Charles Augustus Milverton". The Duke and Duchess were the parents of William Cecil Arthur Clayton, 7th Duke of Greystoke.
The above facts were revealed by Philip José Farmer in Tarzan Alive, which also stated that the Duchess died in 1907. It has more recently been revealed by Win Scott Eckert, who has completed Farmer's unfinished novel The Evil in Pemberley House, that Edith did not die, and that she lived as Dowager Duchess of Greystoke through much of the twentieth century.
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 and Edith Jansenius.