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Kate Middleton pregnant: Second royal baby will be fourth in line to throne
Second-born royal children - often dubbed the "spare to heir" - have on occasion ended up as monarch
The new royal baby will be born fourth in line to the throne.
As a sibling to Prince George, the Duke and Duchess of Cambridge's second child will not be expected to be crowned sovereign.
But second-born royal children - often dubbed the "spare to heir" - have on occasion ended up as monarch.
The country's last king, George VI, was not meant to accede to the throne and only did so when his older brother Edward VIII abdicated over his love for American divorcee Wallis Simpson in 1936.
George VI's father, George V, was also not destined to wear the crown. But he outlived his older brother the Duke of Clarence and Avondale - Prince Albert Victor - who died from flu in 1892. George V became king in 1910.
William and Kate's new baby will be a great-grandchild to the Queen and a great-great-great-great-great-grandchild of Queen Victoria.
Once he or she arrives, Prince Harry will shift down the line of succession to fifth in line to the throne, while the Duke of York will move to sixth place and princesses Beatrice and Eugenie to seventh and eighth.
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The baby will be a prince or princess thanks to the Queen, who stepped in ahead of Prince George's birth to ensure all William's children would become HRHs with fitting titles.
The Queen issued a Letters Patent under the Great Seal of the Realm in December 2012 when Kate was just a few months' pregnant, declaring "all the children of the eldest son of the Prince of Wales should have and enjoy the style, title and attribute of royal highness with the titular dignity of prince or princess prefixed to their Christian names or with such other titles of honour".
A Letters Patent in 1917, issued by George V, limited titles within the royal family, meaning a daughter born to William or Kate would not have been an HRH but Lady (forename) Mountbatten-Windsor instead and a second-born son would also have lacked the HRH title and become Lord (forename) Mountbatten-Windsor rather than a prince.
William's cousin Princess Eugenie, who was born in 1990, was the last royal baby to be given the title Princess. The Earl and Countess of Wessex's daughter Lady Louise Mountbatten-Windsor is also technically a princess, but her parents decided, with the Queen's agreement, that she would use the courtesy title of the daughter of an Earl instead.
If the baby is a girl, it will be the first time a great granddaughter of a still-serving sovereign has been born in direct succession on the male line since 1897, when George VI's sister Princess Mary was born.
