Robert Rassendyll, 1st Earl of Burlesdon, 18th Viscount Rassendyll, was an Englishman nobleman mentioned in The Prisoner of Zenda by Anthony Hope. For legal purposes he was the ancestor of the sixth Earl, but in fact the Earl's mother Amelia had cuckholded her husband the fifth Earl with a visiting European prince. Rudolf Rassendyll was a distant but direct descendant of this union.
In Doc Savage: His Apocalyptic Life, Philip José Farmer reveals that Countess Amelia was herself a descendant of the first Earl, being her husband's second cousin, their earliest common ancestor being the third Earl. He also identifies Lord Dacre as a descendant of the 1st Earl of Burlesdon through Amelia.