(CNN) Britain's Prince William and his wife, Catherine, are expecting their third child together, Kensington Palace announced on Monday.

"Their royal Highnesses The Duke and Duchess of Cambridge are very pleased to announce that The Duchess of Cambridge is expecting their third child," the palace statement read.

"The Queen and members of both families are delighted with the news," it added.

The royal couple with their two children on a three-day tour in Germany on July 21.

As with her two previous pregnancies, Kate is suffering from hyperemesis gravidarum , which involves nausea and vomiting more severe than the typical morning sickness many women suffer during early pregnancy.

The illness has forced Kate, 35, to cancel a planned engagement at the Hornsey Road Children's Centre in London, which had been due to take place on Monday morning. She is being cared for at Kensington Palace, the statement said.