"The Duke of York and Sarah, Duchess of York, Mr and Mrs George Brooksbank, The Queen and The Duke of Edinburgh are delighted with the news", the family wrote on Instagram.
So, when will the happy couple become parents-and when can fans expect to welcome a new royal baby?
However, she'd have to give Jack a title or change the rules on inheriting titles to do that.
It also underwent extensive renovation work over the last few years, so has no doubt been transformed into the flawless starter family home.
Now leading the odds, Arthur is a beloved name among the royal family and is often picked by betters.
Beatrice had a lockdown wedding, marrying Edoardo Mapelli Mozzi in a secret ceremony in Windsor earlier this year.
Eugenie and Jack were invited, and though it's possible the princess was already pregnant, they may not have known.
In addition to the official announcement, Eugenie also shared the news on her own Instagram page.
How is the baby related to the rest of the royals?
The royal family - like most big families - is pretty complex, with several branches and what seems like hundreds of relations. "Welcoming a new baby into the York family is going to be a moment of profound joy". The Duke and Duchess of Gloucester and Prince and Princess Michael of Kent also live within the Kensington Palace complex.
That said, the is another way the child could still get a title and that is only if the queen offers them one for the baby.
The baby will join Prince William and Kate Middleton's children Prince George, Princess Charlotte, and Prince Louis, Prince Harry and Meghan's son Archie Harrison, and the four granddaughters of Princess Anne, Savannah and Isla Phillips, and Mia and Lena Tindall.