Princess Diana and her two daughters-in-law, whom she never met, have a lot in common. Diana Spencer, Kate Middleton and Meghan Markle come from commoner backgrounds who married into royalty. All three are very fashionable, and also the media can’t get enough of them.

But there’s one thing that seemed to separate Diana from her daughters-in-law — she is commonly referred to as Princess Diana, while Kate and Meghan are respectively referred to as Duchess of Cambridge and Duchess of Sussex. Now this got fans thinking why Kate and Meghan can’t be called princesses when both of them married a prince.

Fans can blame their confusion on the rather complicated way that the British use royal titles. Each royal usually accumulates several titles over his lifetime, and it could get too cumbersome to use all of them.

Thus, royals often use one title alone. But the catch is that a royal must use the highest or most senior title that he possesses, according to HuffPost.

Now here’s the confusing part, which most people get wrong — the prince title is actually lower than the royal duke title. “The new Dukedom given by the Monarch supersedes the Princedom already held — a Royal Duke outranks a Royal Prince,” Sallie Smythe wrote on Quora, explaining the royal family’s tradition of granting a royal prince a new royal dukedom on his wedding day.

“When William married, he was elevated from Prince William to Duke of Cambridge,” said Smythe. The same is true with his brother, Prince Henry (Harry), who became the Duke of Sussex.

However, Smythe emphasized that commoners who marry a prince do not actually become princesses. “Non-Royal wives do not ‘become’ Royalty,” she explained. “They are given no titles of their own. They merely earn the right to use the feminine form of their husbands’ highest titles, as long as they are married.”

Since William’s highest title is that of a duke, Kate can be called Her Royal Highness Princess William, Duchess of Cambridge, Countess of Strathearn, Baroness Carrickfergu, according to Huffpost. This can be shortened into Her Royal Highness, The Duchess of Cambridge.

Meghan’s situation is similar to Kate’s. Since Prince Harry’s highest title is the duke title, she is now referred to as the Duchess of Sussex.

“So, marrying Prince Harry won’t technically make Meghan a true princess,” RD wrote. “Technically, she holds the title of Princess Henry of Wales, which is derived from her husband — so she is not a princess in her own right, which one can only be born into.”

Smythe summed up Meghan and Kate’s case nicely when she noted why they only used duchess in their titles. “Technically, Catherine is currently Princess William and Meghan is Princess Henry, but their titles as ‘Duchess’ outrank the former,” the royal expert wrote. Note that they can’t use Princess Kate or Princess Meghan. Instead, they must carry the names of their husbands, which would probably make it even more confusing.

But then why is Diana called Princess Diana? The reason is simple. Apparently, the Prince of Wales title outranks even the royal duke title.

As a result, Diana was able to use the female version of Prince Charles’ highest title. “Diana was styled as HRH, ‘The Princess of Wales’ because it reflected her husband’s highest title: HRH, The Prince of Wales,” Smythe explained.

Later, when she divorced Prince Charles, the HRH and the word “The” were taken out. She was then known as Diana, Princess of Wales.

However, it was reported that even Diana acknowledged that calling her Princess Diana is inaccurate. But the name somehow got stuck in everyone’s mind, and she was mostly referred to by that name.

Meghan Markle and Kate Middleton Catherine, Duchess of Cambridge, and Meghan, the Duchess of Sussex, leave after attending the Commonwealth Service at Westminster Abbey on March 11, 2019, in London, England. Getty Images/Kirsty Wigglesworth-WPA Pool