The media have exploded with the news a married 32-year-old is pregnant.
Before we all drown in endless commentators who are short on facts, here are the five things we know so far about Prince George's little sibling to be.
What We Know About Royal Baby Number Two So Far
It will be fourth in line to the throne(01 of05)
The baby will be behind its grandad, Prince Charles, its dad, Prince William and its brother Prince George. Its uncle Prince Harry will fall to fifth place. (credit:Geoff Pugh/PA Wire)
It will be a Prince or Princess(02 of05)
Yes, yes, this may sound like a dumb thing to say, but it's only the intervention of the Queen that ensured the children of the Cambridges could use these 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". This nullifed a Letters Patent in 1917, issued by George V, which 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 (pictured), who was born in 1990, was the last royal baby to be given the title Princess. (credit:Philip Toscano/PA Wire)
It will be great-great-great-great-great-grandchild of Queen Victoria(03 of05)
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. (credit:Photos.com via Getty Images)
It will be 'spare to the heir'(04 of05)
Unlike Prince George, this Prince or Princess will be free from the responsibility of one day having to become monarch and second-born Royals often have less restricted lives. Prince Harry (pictured) has traditionally been dubbed a party prince in contrast to his older brother William. (credit:Jeremy Selwyn/The Evening Standa/WPA-Rota)
The bookies are already betting on the name(05 of05)
never one to miss a cash-in opportunity - Paddy Power is taking bets on the name. We don't know the sex, but the bookies are saying Elizabeth is the favourite (credit:Twitter)