King George V, by Letters Patent issued on 30 October 1917, declared that henceforward only the children of the Sovereign, the children of sons of the Sovereign, and the eldest living son of the eldest son of The Prince of Wales, would be entitled to the style of Royal Highness and the titles of Prince and Princess. This meant that more distant descendants of the Royal Family had to give up Royal styles. Thus, HH Prince Alastair of Connaught (later the 2nd Duke of Connaught), who was a great-grandson of Queen Victoria, then became known as the Earl of Macduff, a courtesy title belonging to his mother, who was Duchess of Fife in her own right.

On the day before the Duke of Edinburgh’s marriage to The Princess Elizabeth, he was created Royal Highness by Letters Patent:

Whitehall, November 20, 1947.
The KING has been pleased by Letters Patent under the Great Seal of the Realm, bearing date the 19th instant, to declare that Lieutenant Sir Philip Mountbatten, K.G., R.N., shall be entitled to hold and enjoy the style, title and attribute of Royal Highness.

(London Gazette, issue 38128, Nov. 21, 1947, p. 1/5495.)

The children of the Dukes of Gloucester and Kent, as great-grandchildren of a sovereign, do not have Royal attributes. The sons and heirs of the Dukes of Gloucester and Kent therefore bear respectively the courtesy titles of Earl of Ulster and Earl of St Andrews, in the same way as the heirs of other dukes. The younger son and the daughter of the Duke of Kent are known as Lord Nicholas Windsor and Lady Helen Taylor, and the son and daughter of Prince Michael of Kent are known as Lord Frederick and Lady Gabriella Windsor, following the styles for younger sons and daughters of dukes as prescribed by further Letters Patent of 11 Dec 1917.

There has only been one example of children of a Princess and her non-Royal British husband receiving royal titles. When King Edward VII declared his eldest daughter to be The Princess Royal, he instructed Garter King of Arms to declare her two daughters Princesses. Garter is alleged to have told the King that this was impossible as there was no precedent. The King merely told him, “Do it”. Accordingly, the two daughters, subsequently Princess Arthur of Connaught and the Countess of Southesk, were gazetted Princesses with the style of Highness and precedence immediately after all members of the Royal Family bearing the style of Royal Highness. The elder sister attained the style of Royal Highness on her marriage, but the younger ceased to use the style and title on her marriage without any specific declaration being made. It is believed this was to comply with the wishes of King George V, who had not approved of his father’s action.

Before 1977, it was unheard of for a grandson of a Sovereign to be untitled. Peter Phillips, the Queen’s first grandchild, and his sister, Zara, have no titles, since neither of their parents received a peerage, and there is no title to be passed on to their children. It would take a warrant of precedence to raise them to the rank of a son or daughter of a duke or marquess, which would mean they would be at least be in the same position as the son of Prince and Princess Michael of Kent, by having the courtesy style of Lord and Lady respectively, but this did not happen and thus began a change in the practice of royal titles and styles in the current Royal Family.

There have been examples of such precedence being granted by previous sovereigns, such as Lady Katherine Brandram, previously Princess of Greece and Denmark, and Lady Valda Machell, formerly Countess Victoria Gleichen, daughter of Prince Victor of Hohenlohe-Langenburg and granddaughter of Admiral of the Fleet the Hon Sir George Francis Seymour. Brothers and sisters of peers, whose fathers never succeeded, may be given precedence as if their fathers had been peers.