It was announced in April that Prince Harry had officially asked Prince William to be his best man at his wedding to Meghan Markle on May 19.
"Prince Harry has asked his brother The Duke of Cambridge to be his Best Man at his wedding to Ms. Meghan Markle," a Tweet from the palace confirmed at the time.
"The Duke of Cambridge is honoured to have been asked, and is very much looking forward to supporting his brother at St George's Chapel, Windsor on May 19th."
Prince Harry served as best man for William at his wedding to Kate Middleton in 2011.