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Princes William and Harry are hoping to keep their mother's legacy alive by trying "to make a difference" through work that would have made Princess Diana proud.

The princes appeared in the new documentary, "Diana, 7 Days" and revealed how they are trying to fill the void that was left 20 years ago when Diana died in a car crash in Paris. The princes were 15 and 12 years old at the time of their mother's death.

"All I want to do is try and fill the holes my mother has left," Harry, 32, said in the documentary. "And between myself and William, and everybody else that's in those privileged positions, to try and make a difference. And that's what it's about for us, trying to make a difference."

PRINCESS DIANA: HOW SHE HAS BEEN REMEMBERED 20 YEARS AFTER HER DEATH

William, 35, echoed that sentiment, saying he pushed through her tragic death by thinking about what he and Harry can do to make their mother proud.

c2ea8fa1-princess diana garden

Britain's Prince William, center, his wife Kate, Duchess of Cambridge and Prince Harry arrive for an event at the memorial garden in Kensington Palace, London, Wednesday, Aug. 30, 2017. Princes William and Harry are paying tribute to their mother, Princess Diana, on the eve of the 20th anniversary of her death by visiting the Sunken Garden to honor Diana's work with charities. (AP Photo/Kirsty Wigglesworth) (AP)

"Both our parents have brought us up to understand that...there is this element of duty and responsibility that you have to do things you don’t want to do," William said.

He added, "When it becomes that personal, walking behind your mother’s funeral cortege, it goes to another level of duty. But I just kept thinking about what she would want and that she’d be proud of Harry and I. And effectively, she was there with us. It felt like she was walking alongside us to get us through it."

The documentary is set to premiere on Friday.

PHOTOS: PRINCESS DIANA THROUGH THE YEARS

William and Harry have worked at several charities that were close to Diana's heart since she died. Diana was known for taking several causes including HIV/AIDS awareness, homelessness and mental health. She was linked to more than 100 organizations -- many of which her sons have also worked with to continue her work.

Princess Diana Reuters

FILE PHOTO - Britain's Princess Diana holds Prince Harry during a morning picture session at Marivent Palace, where the Prince and Princess of Wales are holidaying as guests of King Juan Carlos and Queen Sofia, in Mallorca, Spain August 9, 1988. REUTERS/Hugh Peralta/File Photo - RTX2XMBU (Reuters)

Thursday marked the 20th anniversary of Diana's death. Harry and William, along with his wife Kate Middleton, Duchess of Cambridge, toured the memorial garden in Kensington Palace on Wednesday. Several celebrities, including Elton John and Piers Morgan, posted tributes on their social media page honoring the late princess.