Prince George and Princess Charlotte will be among the pageboys and bridesmaids at the wedding of Princess Eugenie, Buckingham Palace has said.
The daughter of X Factor judge Robbie Williams, Theodora, will join the young royals in the same role at the wedding.
Princess Eugenie's older sister Princess Beatrice will be maid of honour and groom Jack Brooksbank's brother, Thomas, will be best man.
The couple get married on Friday in Windsor, Berkshire.
Princess Eugenie, 28, who is ninth in line to the throne, became engaged to Mr Brooksbank in January after the couple dated for seven years.
Mr Brooksbank is a former manager of Mayfair club Mahiki and the couple met while skiing.
The other bridesmaids will be: Savannah Philips, seven, the daughter of Autumn and Peter Phillips; Isla Philips, six, the youngest of the Phillips' daughters; Mia Tindall, four, the daughter of Zara Tindall and Mike Tindall; Maud Windsor, five and goddaughter of Princess Eugenie, and daughter of Lady Frederick Windsor and Lord Frederick Windsor.
Louis de Givenchy - the six-year-old son of JP Morgan banking executive Olivier de Givenchy and his wife Zoe - will join Prince George as a pageboy.
The children of the Earl and Countess of Wessex, 14-year-old Lady Louise Mountbatten-Windsor, and 10-year-old Viscount Severn, will take on the role of special attendants.
It has already been announced that 1,200 members of the public have been invited into the grounds of Windsor Castle for the wedding.
Once married, Princess Eugenie and Mr Brooksbank will be taken on a short carriage procession along part of Windsor High Street.
Princess Eugenie, who works in the arts as a director at gallery Hauser and Wirth, is the second daughter of Prince Andrew and Sarah, Duchess of York.