The royal couple named their son Louis Arthur Charles to be known as His Royal Highness Prince Louis of Cambridge.
With her husband on best man duties, Kate will no doubt be on hand to help with her elder children Prince George, four, and Princess Charlotte, three, who have starring roles in the bridal party.
Princess Charlotte joins Harry and Meghan’s goddaughters Florence van Cutsem, Ryan and Remi Litt, Ivy Mulroney and Zalie Warren.
Prince George will be a page boy with Jasper Dyer, Brian and John Mulroney.
Newborn Prince Louis is not expected to attend the wedding.
Look through this gallery to see the best pictures of Kate Middleton, the Duchess of Cambridge, though the years – from her royal wedding in 2011 to the birth of her third child.
Kate Middleton in pictures: Best images of Duchess of Cambridge