AceShowbiz - Prince Harry and Meghan Markle won't be able to pass their royal titles to their future daughters due to old laws of succession. If the couple has any daughter together, they won't be able to call themselves Duchesses of Sussex, nor will they carry on their mother's Scottish title of Countess of Dumbarton or Meghan's Norther Irish moniker, Baroness Kilkeel.

The titles, which the newlyweds received from the Queen on their wedding day, can only be passed on to a future son. The newlyweds' future sons will get to carry on their father's titles of Duke of Sussex, Earl of Dumbarton and Baron Kilkeel.

Back in 2013, Queen Elizabeth II introduced the Succession to the Crown Act. It stated that the next king or queen of the U.K. will be determined by birth order, rather than by gender. With that being said, Prince Louis won't replace the position as fourth in line to the throne which is now retained by his older sister Princess Charlotte.

However, the laws only apply to the direct line to the throne. It explains why Prince Harry and Meghan's future daughters won't inherit their titles. If they have only daughters, their title will automatically die out altogether. According to The Independent, unless the monarch assigns them any more honorary titles, Harry and Meghan's future children will be called Lords and Ladies of Mountbatten-Windsor.

"Under the current system, any child of the Duke and Duchess wont automatically have a royal title," royal commentator Richard Fitzwilliams says. "The peerage, unlike the succession to the crown, favours males and if they have only daughters, the title of Sussex could die out as it did before."

It's different for Prince William and Kate Middleton's children. As he's the oldest son of Prince Charles, his children will all be titled Princes and Princesses.