Thanks to this rule, one of the royal couple's male heirs will not only inherit the title of Duke of Sussex, but also their father's Scottish and Northern Irish titles: Earl of Dumbarton and Baron Kilkeel. And if Harry and Markle have no sons, their royal titles will die out.
What title will the couple's daughters have?
According to Hello magazine, they will be known as Ladies and will only be granted the title of duchess if they marry a duke, as Markle has done. However, Royal Central noted that Queen Elizabeth II has the power to grant hereditary peerage if she wants to.
The Queen has amended outdated royal laws in the past with the approval of the U.K. government and Commonwealth countries.
Most notably, Her Majesty altered the rules of succession, which previously stated all male siblings could jump ahead of their sisters, no matter their birth order. In 2011, 16 Commonwealth countries — including Canada, Australia and Jamaica — voted and agreed to change this law, BBC News reports.
The system was then replaced with absolute primogeniture so that succession would be based on birth order and would not discriminate against female siblings.
This means the Duke and Duchess of Cambridge's daughter, Princess Charlotte, is still fourth-in-line to the throne, despite the birth of her baby brother Prince Louis in April.
Why won't Harry and Markle's future kids be called prince or princess?
The Cambridges' eldest son, Prince George, was the only royal great-grandchild to be guaranteed this title based on the 1917 Letters Patent issued by King George V. However, the Queen updated the letters to allow for all of the Cambridge children to be given the title of prince or princess.
This means Harry and Markle's future children will not receive these titles either, unless the Queen declares it, Time reports.
While the Duke and Duchess of Sussex have not revealed their family plans, they are known for their love of children and have hinted at having kids sooner rather than later.
While viewing baby products during their visit to Belfast, Ireland in March, Markle joked, "I'm sure at some point we'll need the whole lot!"
Being shown a range of innovative baby products at a tech hub in Belfast, Meghan Markle suggests she and Harry will need the lot in the future. pic.twitter.com/NrM0rOJbtM— David Young (@DavidYoungPA) March 23, 2018
CORRECTION: A previous version of this article stated that the Queen can solely make changes to succession and peerage laws. It has been updated to clarify that Her Majesty must get approval from the U.K. government and Commonwealth countries before doing so.
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