Though Kate Middleton is best-known as HRH The Duchess of Cambridge, since marrying Prince William, she instantly became known as England's "future queen" once her husband ascends to the throne.
Although most members of the British royal family have a place in line to be the ruling monarch, it is unlikely that all of them will ever have the opportunity to do so. However, Prince William is pretty sure to have a spot.
Since April 2011, the former commoner Catherine Middleton has been known as Duchess Kate or the Duchess of Cambridge.
Millions of people also assumed that once the Duke of Cambridge becomes king, that also makes Kate an automatic queen.
However, it isn't exactly that simple, according to royal experts.
Kate Middleton will not be Queen but actually will become a queen consort, which is the wife of the ruling monarch.
Since Kate is not a direct descendant of Queen Elizabeth II, the mother-of-three will not have the title "The Queen of England."
Being married to a sovereign doesn't automatically make Kate an official queen.
Only women born into the royal family, such as Kate's daughter, Princess Charlotte, can be called a queen.
As the Queen Consort, Kate Middleton will continue to support her husband all of his duties. Aside from that, she will also make regular appearances around the world and continue to serve as the patron for their charities.
Royal expert Marlene Koenig spoke to Royal Musings blog and explained that she could change one more title in her life if she survives Prince William.
"When Prince George is king, and if Catherine is still alive, she can choose to be styled as HM Queen Catherine, the Queen Mother."
Aside from the Duchess of Cambridge, when in Scotland, Kate Middleton is also known as the Countess of Strathearn, and once in Ireland, she goes by Lady Carrickfergus.
But in her marriage to Prince William, Kate Middleton is a princess.
On her children's birth certificates, Kate Middleton's occupation is listed as "Princess of the United Kingdom."
The media and the public called Princess Diana that way, but her official title was Diana, Princess of Wales, because of her marriage to Prince Charles, the Prince of Wales.
According to royal reports, Queen Elizabeth II can grant Princess titles to those not born automatically as Princesses. However, it is rare in the British royal family.
Though Kate Middleton may not be officially called "Queen Catherine," an insider from her circle claim that she now speaks like the Queen.
According to her unnamed friend, the Duchess of Cambridge has a "ruthless survival streak," which is why she's so suited to life in the Royal Family and is trying to become like Queen Elizabeth II by "modelling herself and speaking like the Queen."
Speaking to Tatler magazine, the source said that Kate "keeps her head down" and is ultimately working towards the goal of becoming Queen.
"In many ways, it's difficult to get a true sense of the real Duchess of Cambridge - so determined does she seem to project an aura of blandness as part of her regal persona."
The source further said, "When I broach the subject, I hear the same sentiments from others, from royal insiders to society figures."
"One member of the young royal set says: 'I've spent quite a lot of time around Kate and she is impenetrable. There is nothing to like or dislike.'"