We're warning you, this is going to get confusing! Once Princess Diana married Prince Charles in 1981, royal fans immediately began calling her a princess. But, how come we don't use the same moniker for Kate Middleton — who also married a prince?

To set the record straight, Kate is a princess even though we don't call her one. On top of that, she is also a Duchess. Yes, she is both a princess and a Duchess! Her full title in England is, "Her Royal Highness Princess William, Duchess of Cambridge, Countess of Strathearn, Baroness Carrickfergu", as the woman takes the man's first name after tying the knot.

Since British nobility has many titles, they often choose to use their "major" one. Keep in mind that the title of a Prince doesn't always trump Duke — Prince William is also called the Duke of Cambridge. As a result, in England, Kate is called Her Royal Highness, The Duchess of Cambridge.

Things were different for Diana when she married Charles because he was a prince in more ways than one. Not only was he born a prince, but in July 1969 he was Invested as Prince of Wales. So as a result, Diana took his major title and went by Diana, Princess of Wales. To top it off, Diana was also born into royalty before marrying Charles!

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Since marrying William, Kate has honored her late mother-in-law in more ways than one. Most notably Kate stood by William's side as he re-dedicated his mom's grave last summer. William previously opened up about his feelings on Diana never being able to meet his family. "I would like to have had her advice. I would love her to have met Catherine and to have seen the children grow up," he confessed. "It makes me sad that she won’t, that they will never know her."

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