Media playback is unsupported on your device Media caption "Revenge is sweet": William on being Harry's best man

Prince William says revenge will be sweet when he becomes Prince Harry's best man next month.

Prince Harry, who is marrying Meghan Markle in Windsor on 19 May, was the best man when the Duke of Cambridge married Kate Middleton in 2011.

Prince Harry also joked with reporters stating that he had got down on one knee to ask his brother, who said he was "thrilled" to be asked.

Prince William said he was "working on" a name for his three-day old son.

Prince William and Catherine's third child, who was born on Monday weighing 8lb 7oz, is fifth in line to the throne.

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Before his brother's wedding in 2011, Prince Harry said his best man's speech would "dig (Prince William) in the ribs a few times and embarrass him" and "make him lose some hair".

In an interview with Rio Ferdinand in January, Prince William joked that his brother had not yet asked him to be the best man and "it could be a sensitive issue".

Media playback is unsupported on your device Media caption Prince Harry joked about being Prince William's best man in 2011

More than 600 guests have been invited to the wedding ceremony at St George's Chapel with 1,000 members of the public being welcomed to the grounds of Windsor Castle.

A further 200 guests - including the Spice Girls - have been invited to the couple's evening reception.

Image copyright Getty Images Image caption Prince Harry will marry Meghan Markle on 19 May in Windsor

In a statement, Kensington Palace said: "The Duke of Cambridge is honoured to have been asked, and is very much looking forward to supporting his brother."

The palace also tweeted a picture of the pair of Princes when they were boys wearing police helmets.

Image copyright PA Image caption Kensington Palace shared a picture of the two princes as boys

Earlier this week, the palace announced the list of musicians who will be playing at the wedding.

They include a gospel choir and 19-year-old cellist Sheku Kanneh-Mason, who won the 2016 BBC's Young Musician.

Media playback is unsupported on your device Media caption Hopefully Prince William will have had a chance to catch up on his sleep following the birth of his third child by the wedding in May

The May wedding will be the second time within a month to see Ms Markle as a bride.

The actor's exit from the series Suits was shown on TV on Wednesday with her character getting married.

Image copyright PA Wire Image caption Prince William is returning the favour after his younger brother was best man at his wedding in 2011

Image copyright PA Image caption Prince William helped send his three-year-old brother off to Kindergarten in 1987

Image copyright Martin Keene/PA Wire Image caption The brothers toured the Canadian frigate HMCS Ottawa together in 1991

Image copyright Martin Keene/PA Wire Image caption That same year they visited the Royal Yacht Britannia

Image copyright Barry Batchelor/PA Wire Image caption In 2002 the two princes were rivals in a bicycle polo match

Image copyright Stefan Rousseau/PA Wire Image caption They were pictured together again in 2002 at the royal box for the second concert to commemorate the Golden Jubilee of the Queen

Image copyright Andrew Parsons/PA Wire Image caption They spent their Christmas in 2003 at Sandringham

Image copyright Andrew Parsons/PA Wire Image caption In 2005 they attended the marriage of Prince Charles and Camilla Parker Bowles