Prince William and Kate Middleton, The Duke and Duchess of Cambridge, are expecting their second child together.

Duke & Duchess Pregnant

Middleton’s pregnancy was announced by Clarence House on Monday. As with her first pregnancy, Middleton’s struggle with hyperemesis gravidarum – a severe form of morning sickness – led to the baby news breaking, reported CNN. She was forced to cancel a planned official engagement in order to receive treatment for the condition at Kensington Palace.

The royal couple is reportedly “delighted” that they’ll soon be giving Prince George a younger brother or sister.

“The Queen and members of both families are delighted with the news," a statement from Buckingham Palace read. The due date and sex of the child have not yet been revealed.

Among the many congratulating the Duke and Duchess, 32, was British Prime Minister David Cameron, who took to Twitter to share his excitement about the baby news.

Many congratulations to the Duke and Duchess of Cambridge. I'm delighted by the happy news that they're expecting another baby.

— David Cameron (@David_Cameron) September 8, 2014

Prince George’s younger sibling will become fourth in line to the throne. Prince Charles is currently first in line, followed by Prince William. With the birth of his brother’s second child, Prince Harry will become fifth in line to the throne.

The Duke and Duchess welcomed Prince George in July 2013.