09/04/2017 06:51 EDT | Updated 09/04/2017 09:31 EDT

Duchess Of Cambridge, Prince William Expecting Their Third Child, Kensington Palace Says

A sibling for George and Charlotte!

Catherine, Duchess of Cambridge, Prince William, Prince George and Princess Charlotte wave to wellwishers as they depart Victoria on October 1, 2016 in Victoria, B.C. (Photo: Samir Hussein/WireImage)

Fantastic news for this holiday Monday, royal watchers: Kate is pregnant again!

That's right, the Duke and Duchess of Cambridge are expecting their third child, Kensington Palace said early Monday.

Watch more in the video below:

The Palace made the pregnancy announcement as they said that the former Kate Middleton was not feeling well enough to attend an engagement later in the day. As with her other two pregnancies, the duchess is suffering from Hyperemesis Gravidarum, or acute morning sickness.

"The queen and members of both families are delighted with the news," the palace said in a statement.

Kate is being cared for at her Kensington Palace home in London.

William and Kate, both 35, already have two children: Prince George, 4, and Princess Charlotte, 2.

The announcement came at a time when the royal couple is due to mark a milestone in the life of their young family: They are set to send George to school for the first time on Thursday.

Their choice of Thomas's Battersea in south London indicated that the Cambridges were settling into their Kensington Palace apartment, having moved recently from their Norfolk home Anmer Hall.

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Prince George of Cambridge at the Berlin Tegel Airport on July 19, 2017, in Berlin, Germany. (Photo: DMC/GC Images)

Rumours had swirled about another pregnancy for Kate when reports surfaced that she had been rushed to the hospital earlier in August.

No details were immediately available about when the third baby is due, but betting agencies were quick to start offering odds on possible names for the soon-to-be-born child in the House of Windsor.

Paddy Power offered 8-to-1 odds on Alice. Also popular was Diana, after Prince William's mother, particularly given the timing of the announcement.

Max Mumby/Indigo via Getty Images
Prince William views tributes to Diana, Princess of Wales left at the gates of Kensington Palace after visiting the Sunken Garden on August 30, 2017 in London, England. The Sunken Garden has been transformed into a White Garden dedicated to Diana, Princess of Wales mother of The Duke of Cambridge and Prince Harry marking the 20th anniversary of her death. (Photo: Max Mumby/Indigo/Getty Images)

Together with Prince Harry, William and Kate have taken a leading role in marking the 20th anniversary of Diana's death. Last week the royals toured the garden of their Kensington Palace home to remember the princes' mother and celebrate her contributions to their family and to the monarchy.

"Given the recent anniversary, there'll be plenty of interest in the name Diana if the baby is a girl,'' the agency said.

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Will it be another girl? Princess Charlotte and mum Kate arrive at Warsaw airport on July 17, 2017 in Warsaw, Poland. (Photo: Karwai Tang/WireImage)

The royals have said from the time of their engagement that they wanted to have a family — the only question was how many children they wished for. Royal watchers recorded every aside for clues as to what the plans might be.

When asked on a royal tour in Singapore in 2012 about how many children he wanted, William said he was "thinking about having two."

More recently, during a royal tour of Poland, Kate joked about a third child when given a cuddly toy designed to soothe tiny babies.

Kate is the eldest of three siblings, and reportedly had a very happy childhood. William has a younger brother, Prince Harry, who is now sixth in line for the throne, with the Kate and William's upcoming third child fifth in line.

And as for Harry, royalphiles are eagerly hoping for a big announcement from his side: his engagement to Toronto-based girlfriend and "Suits" star Meghan Markle. The couple was recently on holiday together in Botswana, sparking rumours Harry may pop the question soon.

But for now, let's just let this pregnancy announcement sink in, shall we? Congratulations, William and Kate!

With files from Lisa Yeung.

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