From the CC:
The Prince of Wales was accompanied by The Duke of Cambridge (Colonel, Irish Guards) and The Princess Royal (Gold Stick and Colonel, The Blues and Royals, Royal Horse Guards and 1st Dragoons).
The Duchess of Cornwall, The Duchess of Cambridge with Prince George of Cambridge, Princess Charlotte of Cambridge and Prince Louis of Cambridge, The Duke and Duchess of Sussex, Princess Beatrice, Mrs Edoardo Mapelli Mozzi and Mr Edoardo Mapelli Mozzi, Princess Eugenie, Mrs Jack Brooksbank and Mr Jack Brooksbank, The Earl and Countess of Wessex with The Lady Louise Mountbatten-Windsor and Viscount Severn, The Duke and Duchess of Gloucester, The Duke of Kent (Colonel, Scots Guards), Prince and Princess Michael of Kent, Princess Alexandra, the Hon Lady Ogilvy, Vice-Admiral Sir Tim Laurence and other Members of the Royal Family drove to Horse Guards Parade and witnessed The Queen’s Birthday Parade.
On arrival at Buckingham Palace, The Queen’s Guard entered the Forecourt and formed up opposite the Old Guard, the remaining Guards marching past Her Majesty, accompanied by The Duke of Kent.