Curators of the exhibition announced on Monday the brothers had agreed to allow Diana's gown to be included as the centrepiece of the new exhibit called Royal Style in the Making, which opens on June 3 in the Orangery of Kensington Palace.
It's the first time the wedding dress, which was designed by Elizabeth and David Emanuel, will be on display at the palace in 25 years.
The exhibit will show the relationship between fashion designers and their royal clients over the years. It will also feature other important and never-before-seen historical pieces.
Speaking to People, Elizabeth Emanuel said seeing the gown she designed at the exhibition "will be like seeing an old friend after all these years. I was looking at the images again today and I can't believe how many sequins we sewed on to the dress. This is going to be a wonderful exhibition."
The dress features the longest train in royal history measuring 25 feet, almost eight metres, which is covered in sequins. Some of the dress was also made using antique Carrickmacross lace which originally belonged to Prince Charles' great-grandmother, Queen Mary.
The exhibition will kick off a number of commemorative events in honour of what would have been Princess Diana's 60th birthday on July 1, this is when a statue of the late royal will be unveiled.
William and Harry commissioned a statue of their mother to be installed at Kensington Palace to mark the 20th anniversary of Diana's death "and recognise her positive impact in the UK and around the world".
The gown was turned over to Harry and William by Diana's brother Charles Spencer, who had looked after the gown for 17 years until Harry's 30th birthday.
Diana had directed in her will for the gown to be transferred to her children when her youngest turned 30.
Harry was reportedly so "shocked" by the "very, very cold reception" he received from the royal family after he arrived for Prince Philip's funeral that he might cancel his upcoming trip for the unveiling of his mother's statue.
"Some quarters of the family did give him a frosty reception and perhaps that did shock him somewhat," Russell Myers told talkRADIO, adding the birth of Harry and Meghan Markle's second baby could provide a "convenient excuse" not to "face the family"
Russell added, "I'm told he is still committed to coming. Both camps are. Certainly, Kate and William will welcome him if he wants to come back.
"His intention is to come back. One may wonder, if his wife has just had a baby, I'm sure he could jump on a private jet and make a flying visit.
"But, will it be a convenient excuse so he doesn't have to come back and face the family?"
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