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.
List of viscountcies in the peerages of Britain and Ireland
Viscounts were created in the peerages of England and Scotland until the Act of Union 1707, thereafter being created in the peerage of Great Britain. After the Acts of Union 1800 came into effect in 1801, all peerages were created in the Peerage of the United Kingdom. Viscounts in the Peerage of Ireland were created by English and British monarchs in their capacity as Lord or King of Ireland. Irish peers were not initially granted a seat in the House of Lords and so allowed the grantee to sit in the House of Commons. Viscounts of Ireland have precedence below peers of England, Scotland, and Great Britain of the same rank, and above peers of the United Kingdom of the same rank; but Irish peers created after 1801 yield to United Kingdom peers of earlier creation.