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.
Barons in Scotland
An English barony is a peerage (yet the abolition act of 1660 allows for some remaining non-peer baronies not converted by writ to remain as feudal baronies of free socage "incorporeal hereditament" similar to a lordship of the manor), but whether Scottish barons rightfully rank as peers is disputable. They are known as minor barons currently treated as noble titles of less than peerage rank. The Scottish equivalent of an English baron is "Lord of Parliament".