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.
Privilege of peerage
The privilege of peerage extends to all temporal peers and peeresses regardless of their position in relation to the House of Lords. The right to sit in the House is separate from the privilege, and is held by only some peers (see History of reform of the House of Lords). Scottish peers from the Acts of Union 1707 and Irish peers from the Act of Union 1800, therefore, have the privilege of peerage. From 1800, Irish peers have had the right to stand for election to the United Kingdom House of Commons but they lose the privilege of peerage for the duration of their service in the lower House. Since 1999, hereditary peers of England, Scotland, Great Britain, and the United Kingdom who are not members of the House of Lords may stand for election to the House of Commons. Their privilege of peerage is not explicitly lost by service in the lower House. Any peer issuing a disclaimer under the provisions of the Peerage Act 1963 loses all privileges of peerage. The privilege of peerage also extends to wives and widows of peers. A peeress by marriage loses the privilege upon marrying a commoner, but a peeress "suo jure" does not. Individuals who hold courtesy titles, however, do not have such privileges by virtue of those titles. Lords Spiritual (the 26 Archbishops and Bishops who sit in the House of Lords) do not have the privilege of peerage as, at least since 1621, they have been Lords of Parliament, and not peers.