Royal dukedoms in the United Kingdom
In the British peerage, a royal duke is a member of the British royal family, entitled to the titular dignity of prince and the style of "His Royal Highness" who holds a dukedom. Dukedoms are the highest titles in the British roll of peerage and the holders of these particular dukedoms are Princes of the Blood Royal. The holders of the dukedoms are royal not the titles themselves. They are titles created and bestowed on legitimate sons and male-line grandsons of the British monarch, usually upon reaching their majority or marriage. The titles can be inherited but cease to be called "royal" once they pass beyond the grandsons of a monarch. As with any peerage, once the title becomes extinct, it may subsequently be recreated by the reigning monarch at any time.
Earl Cowper
Earl Cowper (pronounced "Cooper") was a title in the Peerage of Great Britain. It was created in 1718 by George I for William Cowper, 1st Baron Cowper, his first Lord Chancellor, with remainder in default of male issue of his own to his younger brother, Spencer Cowper. Cowper had already been created Baron Cowper of Wingham in the County of Kent, in the Peerage of England on 14 December 1706, with normal remainder to the heirs male of his body, and was made Viscount Fordwich, in the County of Kent, at the same time as he was given the earldom, also Peerage of Great Britain and with similar remainder. He was the great-grandson of William Cowper, who was created a Baronet, of Ratling Court in the County of Kent, in the Baronetage of England on 4 March 1642. The latter was succeeded by his grandson, the second Baronet. He represented Hertford in Parliament. He was succeeded by his eldest son, the aforementioned William Cowper, the third Baronet, who was elevated to the peerage as Baron Cowper in 1706 and made Earl Cowper in 1718. In 1706 Lord Cowper married as his second wife Mary Clavering, daughter of John Clavering, of Chopwell, County Durham.