Kate Middleton typically goes by the title, The Duchess of Cambridge. But Kate was listed as Princess of the United Kingdom. The Royals make it clear that Kate Middleton should not be known as Princess Catherine. Since the ‘British Royal Titles’ can be confusing, here’s a guide.
Through marriage, Kate Middleton is ‘Princess William’. As Middleton takes the female form of her husband, Prince William’s titles.
Despite this Royal title being held through marriage, it’s certainly unlikely that Kate Middleton will ever be made a ‘Princess’ in her own right.
According to the laws…
Those who marry into The Royal Families are by default made ‘prince’ or ‘princess’ in their own right. However, this system is not used in the United Kingdom. Where custom and usage has evolved so that the title is almost invariably only given to Royals by birth or ‘Blood Royals’.
In 2012, Queen Elizabeth created a new letters patent which grants the title to all children of the eldest son of the Prince of Wales. In practice, this part means that all children of Prince William will be given the title of Prince and Princess now.
Another side of this is the question what about when William is Prince of Wales?. If and when the title of Prince of Wales will be granted to Prince William after Prince Charles becomes King. He would simply become HRH The Prince of Wales. Whilst Catherine currently Duchess of Cambridge would adopt the title of ‘HRH The Princess of Wales’. But this would still not make her ‘Princess Catherine’. Also, the title of Princess of Wales’ is not the same as Princess.
Even though people refer Diana, Princess of Wales ‘Princess Diana’, she never actually held that title. It was used by many as a shortened one. The same applies to Kate Middleton only if she becomes Princess of Wales.
So according to the things now, The Duchess of Cambridge will never become a ‘Princess’ in her own right. There’s no precedent for affording the title to Royals in her place and there’s no reason to think that this tradition will be broken anytime soon or we can say at all.