Princess Anne with her brothers, Charles, Andrew and Edward at the Garter Service, Windsor , 2006

 The Princess Royal, The Earl of Wessex, The Duke of York and The Prince of Wales in procession to St George's Chapel, Windsor Castle for the annual service of the Order of the Garter. This was the first occasion on which all four of Queen Elizabeth's children had attended the Garter Service, following the appointment of the Duke of York and the Earl of Wessex to the Order in April 2006.

Source: wikipedia.com