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It'll be almost 21 years since Princess Diana died, but her brother, Charles Spencer, continues to remember her legacy.

In a new interview with People Magazine published on Thursday, Spencer admitted that out of all the heatbreaks of his sister's early death, the one that sticks out the most to him is knowing that Diana will never meet her grandchildren, Prince George, 5, Princess Charlotte, 3, and Prince Louis, 4 months.

"One of the great tragedies is that Diana would have been the best grandmother ever,” Spencer told the outlet.

However, Spencer is happy that he gets to see Diana's memory live on through her sons, Prince William and Prince Harry.

“I love seeing the sort of uncomplicated way that they deal with people, and put them at their ease,” he shared, adding that “It’s so easy to connect the dots between them and their mother.”

Reuters Princess Diana Prince Harry

Reuters (Princess Diana with Prince Harry.)

Princess Diana of Wales died at a Paris hospital following a car crash on August 31, 1997. She was 36.

“What’s amazing to me is the passing of time,” admits Spencer, noting that Prince William and wife, Kate Middleton, both 36, "are nearly the same age as Diana when she died."

princess diana william reuters

Princess Diana with Prince William. (Reuters)

He continues: “I love the fact that there’s still such veneration inside her immediate family for what she was, and what she meant. I think that’s fantastic.”

Looking back on the tragic day though, Spencer tells the magazine that at the time, he couldn't help but think that there was something he could have done.

“I was furious, I wasn’t just angry,” he explained. “[I thought] what could I have done. But you always think, God, I wish I could’ve protected her. It was just… it was devastating.”

"I always felt…intensely protective towards her," Spencer admits.

As for why he's speaking about his late sister now?

“One of the reasons I wanted to talk now is because I think after 20 years, someone shifts from being a contemporary person to a person of history actually,” he shared. “And Diana deserves a place in history.”

“I think that it’s important for people who are under 35, who probably won’t remember her at all, to remember that this is a special person. Not just a beautiful one.”