Meghan Markle and Prince Harry’s eldest child Archie, under the Letters Patent, is eligible to be known as His Royal Highness Prince Archie of Sussex, while Lilibet may be styled as Her Royal Highness Princess Lilibet of Sussex.
King George V issued the Letters Patent in 1917, which determines who receives a royal title within the royal family.
When Lilibet and Archie were born, they were great-grandchildren of Queen Elizabeth II, meaning they couldn’t be a prince or princess. But now King Charles III has started his reign and there have been several major title changes for them.
However, it remains to be seen whether the royal children will use their titles in the future or remain Master and Miss.
King George V issued a Letters Patent in 1917 to limit who could bear a royal title, and apart from the children and grandchildren of the monarch through the male line, only the eldest son of the eldest son of the Prince of Wales entered eligible for a Prince or Princess title.
The late Queen Elizabeth II reportedly changed this rule to include all children of the Prince of Wales’ eldest son. For this reason, all Cambridge children have the title of Prince or Princess, whereas previously only Prince George would qualify.