Any children born to Prince Harry and Meghan Markle will be a lord or lady, not a prince or princess - unless the Queen steps in.
Titles within the royal family were limited by Harry's great-great-grandfather King George V, who issued a Letters Patent in 1917.
It read: “...the grandchildren of the sons of any such Sovereign in the direct male line (save only the eldest living son of the eldest son of the Prince of Wales) shall have and enjoy in all occasions the style and title enjoyed by the children of Dukes of these Our Realms.”
This means Harry and Meghan's children, should they have any while Elizabeth II is on the throne, will not be HRHs or princes or princesses, but will be known instead as Lord or Lady (forename) Mountbatten-Windsor.
However the Queen could issue a new Letters Patent to change this - just as she did for the Duke and Duchess of Cambridge's children.
George was always entitled to be HRH Prince George of Cambridge as the eldest son of the eldest son of the Prince of Wales. But HRH Princess Charlotte of Cambridge would have been Lady Charlotte Mounbatten-Windsor.
In December 2012, when Kate was around three months pregnant, the Queen issued a Letters Patent under the Great Seal of the Realm declaring “all the children of the eldest son of the Prince of Wales should have and enjoy the style, title and attribute of royal highness with the titular dignity of Prince or Princess prefixed to their Christian names or with such other titles of honour”.
A Letters Patent was granted in 1948 just before the Prince of Wales's birth because the 1917 decree excluded Princess Elizabeth's children from taking a royal style and title.
The Princess Royal's children, Peter and Zara Phillips, who do not hold titles, were Master and Miss Phillips when they were born. They were not entitled to be HRHs under the 1917 decree as they were born down the female line.
The Earl and Countess of Wessex's children, Lady Louise Mountbatten-Windsor and Viscount Severn, are actually entitled to be a princess and prince as children of the son of the Sovereign.
But Edward and Sophie decided, with the Queen's agreement, that their children would use the courtesy titles of sons or daughters of an earl rather than the style prince or princess.
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