Prince William is notoriously reserved about his mother, Princess Diana, who died in a car crash in 1997 when he was just 15.
But during a visit to a charity in Stratford, London, he opened up about grieving to a 9-year-old who lost her father to pancreatic cancer six years ago.
"Do you know what happened to me?" William told Aoife. "You know I lost my mummy when I was very young too. I was  and my brother was 12. So we lost our mummy when we were young as well.
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He then asked the girl: "Do you speak about your daddy? It's very important to talk about it. Very, very important."
The Duke and Duchess of Cambridge, Kate, met kids at the Child Bereavement UK Centre, a charity that helps families deal with the loss of a loved one, which was founded in 1994 by one of Diana's closest friends, Julia Samuel.
Along with Prince Harry, William and Kate have focused their activities on mental health awareness.
William admitted he was very angry after Diana died, almost 20 years ago.
"He told us how he felt angry when she died. He very specifically used that word anger, he felt angry about it," a mum who was at the event said.
In July last year, Prince Harry told Rio Ferdinand, the former England and Manchester United footballer who lost his wife last year, that he regretted not opening up sooner about his mother's death.
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