Prince Harry has been chosen as his brother's best man and Kate Middleton's sister Philippa will be her maid of honour at the British royal wedding on April 29.
Prince Charles's office made the announcement Monday, ending weeks of speculation.
Prince William and Middleton also named a number of bridesmaids and page boys for the nuptials at Westminster Abbey.
The bridesmaids include Lady Louise Windsor, 7, the daughter of the Earl and Countess of Wessex; Margarita Armstrong-Jones, 8, the daughter of Viscount and Viscountess Linley; Eliza Lopes, 3, daughter of Harry Lopes and Camilla Parker Bowles's daughter, Laura; and Grace van Cutsem, 3, a godchild of William's.
Page boys for the wedding will be William Lowther-Pinkerton, 10, the son of William's private secretary, and Tom Pettifer, 8, another of William's godchildren.
Officials said details about the bridesmaids' dresses and the page boys' uniforms will be made available on the wedding day.
William and Middleton will be married by Archbishop of Canterbury Rowan Williams.
Middleton will travel to the 11 a.m. wedding service at Westminster Abbey in London by car along a route that will include The Mall, Horse Guards Parade, Whitehall and Parliament Square.
The dean of Westminster, Very Rev. John Hall, will conduct the service, while Bishop of London Richard Chartres will give an address.
The newlyweds will then travel in a carriage procession to Buckingham Palace, retracing the same London landmarks that Middleton passed on her way to the abbey.
At Buckingham Palace, Queen Elizabeth will host a reception for the couple and invited guests.
Prince Charles will give a private dinner and dance in the evening at the palace.[GALLERY id=4109 cat=news]