It has been almost 20 years since Princess Diana was tragically killed in a car accident in Paris, and her family continues to pay tribute to her life.

During a documentary her sons, Prince William and Prince Harry reveal the regret they carry after their last phone call with their mom the day she died.

In the 90 minute program, we get a glimpse into the home of Diana and her family.

"Our mother was a total kid through and through.When everybody says to me 'so she was fun, give us an example' all I can hear is her laugh in my head. One of her mottos to me was, 'you can be as naughty as you want, just don't get caught.' She was one of the naughtiest parents. She would come and watch us play football and, you know, smuggle sweets into our socks," Harry said.

In addition to the documentary, the Princes have released photos from a private family album that have never before been seen.

"The Duke and Prince Harry are pleased to share 3 photographs from the personal photo album of the late Diana, Princess of Wales," Kensington Palace wrote on their Twitter page.

When looking through the photographs, Prince William spoke of the photo of his mother wearing a sweater and carrying him as a toddler. Talking to Prince Harry, he said, "Believe it or not, we're both in this picture, you're in the tummy."

As the anniversary of Princess Diana's death approaches, Kensington Palace is sure to release further tributes, photographs and stories honoring Prince William and Harry's mom.

This includes a documentary that revealed that the boys regret their last phone call with their mother. Find out why on the next page.

Prince William and Prince Harry have spoken of their enduring regret of their last conversation with their mother Princess Diana before her death in 1997.

The Duke of Cambridge and his younger brother, who were ages 15 and 12 at the time, were in Balmoral with their cousins when their mother was killed in the car accident.

"All I do remember is probably regretting for the rest of my life how short the phone call was," Prince Harry says in an ITV documentary.

After Diana and Prince Charles divorced in August of 1996, Harry admits that they spent far too much time speaking on the phone, rather than in person.

"At the time Harry and I were running around minding our own business, you know, playing with our cousins and having a very good time," William recalled.

"As a kid, I never enjoyed speaking to my parents on the phone," Prince Harry continued. "And we spent far too much time speaking on the phone rather than speaking to each other, because of just the way the situation [the divorce] was."

"And the phone rang and off he [William] went to go and speak to her sort of for five minutes."

William went on: "And I think Harry and I were just in a desperate rush to say goodbye, you know, see you later and we're going to go off."

Prince William revealed that he remembered the conversation for all these years, but did not want to disclose it until now.

"If I'd known now obviously what was going to happen, I wouldn't have been so blasé about it and everything else. But that phone call sticks in my mind quite, quite heavily."

Prince Harry added: "I can't really necessarily remember what I said, but all I do remember is probably, you know, regretting for the rest of my life how short the phone call was."

"And if I'd known that that was the last time I was going to speak to my mother. the things I would have said to her. Looking back on it now, it's incredibly hard. I have to sort of deal with that for the rest of my life."

"Not knowing that that was the last time I was going to speak to my mum, and how differently that conversation would have panned out if I'd had even the slightest inkling that her life was going to be taken that night."

The princes are joined in the 90-minute video by some of Diana's close friends and family members, including singer Sir Elton John.

William said that he and his brother felt that this was the right time to share their very personal memories of life with their mom.

"I think Harry and I feel very strongly that we want to celebrate her life and this is a tribute from her sons to her," William said.

Diana, Our Mother: Her Life and Legacy airs Monday, July 24 at 10PM on HBO.

Sources: Good Housekeeping / Good Housekeeping