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Prince William and Duchess Kate Middleton are expecting their third child

Logan Sowa

The Duke and Duchess of Cambridge, Kate Middleton and Prince William, are expecting their third child, Kensington Palace announced Monday.

"The Queen and members of both families are delighted with the news," the Palace said.

Prince William and Duchess Kate's love story:

Kate is once again suffering from extreme morning sickness, Hyperemesis Gravidarum, which ailed her first two pregnancies as well. She had been planning to carry out an engagement today at the Hornsey Road Children's Centre in London, but cancelled it due to her illness.

The Duchess is being cared for at Kensington Palace.

The last time we saw Kate was during a visit to the White Garden with William and Harry to commemorate Princess Diana's life and loss. She may have already been suffering from her illness but clearly wanted to be there with her husband and brother-in-law to remember their late mother.

Kate and William's two little ones, George and Charlotte, are 4 and 2. Soon to be a big brother again, Prince George starts his first day of school at Thomas's Battersea on Thursday September 7th. If Kate is feeling up to it, she and William had planned to take George to his first day.

See photos of Prince George and Princess Charlotte: