] Your explanation makes it very clear, and if I follow you correctly, the present day Prince of Wales and Duke of York are family titles which Queen Elizabeth II would hold thus they are hers to grant. Following this line of thought then, would Prince Charles, upon assumption of the throne, have the right to revoke his brother's use of the title Duke of York, since he has assumed the monarch's position?

I don't belive Prince Charles when he becomes King, would be able to revoke the Duke of Yorks title, just because he wanted to. There are several titles that are traditionally give to the children of a monarch. While it is for the monarch to decide when and where their offspring receive these new titles, the titles themselves are part of a strict royal tradition. They are not given out, or taken away, easily or on a whim, unless the titleholder intentionally renounces the title (as King Edward did ).

The titles are usually given out by the monarch, when the child comes of age, marries or does something of note that especailly pleases their parents. The most well known of these honorary titles are that of the heir to the throne, who becomes the Prince of Wales, the eldest daughter who becomes the Princess Royal, the second son who becomes the Duke of York and the third son who becomes the Duke of Kent.

There have been several rather significant Dukes of York and Kent, The last Duke of York was the father of the present queen. His parents were so thrilled at his choice of bride ( the recently deceased Queen Mother ) that their wedding present to their second son, was the "new" title of Duke of York. A previous Duke of Kent was also the father of Queen Victoria. So you see, these titles are very old and can't be messed with by a new monarch, just because he feels like it.

As to stripping a titled noble of his rank against his will, it is not easy to do. In the grand old English tradition of primogenture, the eldest son of the Duke of Marlbourough, will one day inheirit the Dukedom and the ancestral estate of Blenheim Palace ( which gets a mention in P&P I belive ). However, this young man ( the Marquess of Blandford ) is a drug addict and a wastrel. His father is very worried that the title and management of the ancestral estate, will one day be in the hands of someone incapable of looking after it. So the Duke went to the House of Lords and the Royal College of Arms, to see if he could get the eldest sons titles invalidated and have his much more reliable second son installed as the heir instead. As rich and powerful as the Duke is, he was told "No can do" as to do so, would mean a new act of Parliament that no-one was willing to sponsor, as it would set a dangerous precendent of messing with a system of titles that had been around 1000 years.

The Duke of Marlborough is a non royal Duke but I don't think an actual royal personage would have any better luck. A monarch can refuse a title to be granted in the first place, but I don't believe it can be taken away, once granted, unless it was intentionally renounced. It probably could be taken away back in the days of King Henry when he ruled supreme, but Parliament and the House of Lords has a say in these things these days and, I can't see them going for it. If Prince/King Charles wants to give the title of Duke of York to his own second son, he is probably going to have to wait until the present incumbant passes away.

Then again, when Prince Charles and Diana divorced, she got to keep her title of Princess of Wales but she lost her royal status of "HRH" as did the Duchess of York. So who really knows about the Duke of York thing ? There are a lot of strange and weird things happening with the royals these days.....LOL