The Order of Service has revealed Prince William and Princess Kate's son Louis, five, will appear alongside his siblings, Prince George, nine, and Princess Charlotte, eight, during the ceremony.
The Sun reports Louis will take part in the Procession of The King and Queen, Camilla, from Westminster Abbey alongside his sister after the two-hour ceremony.
Meanwhile, George, who is one of the King's Pages of Honour, will become the youngest future king to have a major role in a coronation.
George, Charlotte and Louis will also ride and wave to crowds in a carriage behind the Gold State Coach of the King and Queen during the 2km Coronation Procession to Buckingham Palace.
Unlike Prince Harry, Louis will also make an appearance on the Buckingham Palace balcony with his parents and siblings.
Kate updated royal fans during a walk in central London, sharing the children have taken part in rehearsals, "Having done a few, [rehearsals], I think everyone is a bit more relaxed."
While Louis has been included on the coronation program, Kate and William will make an official decision of his attendance before the ceremony.
Prince Harry and Prince Andrew both have no role in the coronation, and will not appear in any carriages or processions.
They will be seated in the third row, away from senior members of the royal family in the first row.
"There were discussions that the seating could be arranged on line of succession," a source revealed to The Sun. "But that would have put fifth-in-line Harry front and centre – and with William and Kate.
"Instead the decision was working royals only at the front and work back from there. Harry will be a long way from his father."
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