Kate Middleton and Meghan Markle are not called princesses because of Queen Elizabeth II. A royal expert clarified that the decision has nothing to do with Camilla Parker Bowles.

Victoria Arbiter told Yahoo’s “The Royal Box” that Camilla is legally known as the Princess of Wales after she married Prince Charles. But the mom of two decided to not take the title because the public considers the late Princess Diana as the Princess of Wales despite her divorce from Prince Charles.

Years later, Kate decided to go with the royal title of Duchess of Cambridge and not Princess Kate even though she will also become queen one day. Meghan is also known as the Duchess of Sussex even though her husband’s official title has a prince in it.

“That’s why it’s Duchess throughout the royal family — because Camilla is a Duchess,” Arbiter said. “Had the Queen not conferred the wedding day dukedoms on William and Harry, their wives would have been known as Princess William of Wales and Princess Henry of Wales in the same way Baroness Marie Christine von Reibnitz became Princess Michael of Kent upon her 1978 marriage to Prince Michael,” Arbiter added.

In her article for Honey Nine-Nine, the royal commentator also said that decisions regarding royal titles are solely at Her Majesty’s discretion and not Camilla. The stylings of the members of the royal family are steeped in centuries of royal history, and the only person who can implement changes is the sovereign.

“Should the Queen choose to do either, her decrees are based on a number of factors including changes that have been made to existing royal rules, a long-standing tradition, and the examples set by kings and queens who have gone before her,” she said.

Arbiter also said that one day Kate Middleton will be known as the Princess of Wales or the queen consort when Prince William becomes king. Meghan, on the other hand, will seal her place in history as the first ever Duchess of Sussex.

Kate Middleton and Meghan Markle Catherine, Duchess of Cambridge, and Meghan, Duchess of Sussex, arrive to attend Christmas Day Church service at Church of St Mary Magdalene on the Sandringham estate on Dec. 25, 2018, in King's Lynn, England. Stephen Pond/Getty Images