The 37-year-old royal lost his mother when he was a teenager after she died in a car crash in 1997, and whilst his own children - Prince George, six, Princess Charlotte, five, and Prince Louis, two, whom he has with his wife Catherine, Duchess of Sussex - have never met their grandmother, William makes sure they know all about her.
Royal commentator Katie Nicholl said: ''William is keeping his mother's memory alive. They have photos of Diana around the house, very deliberately so, and he speaks about her to the children.
''He and Kate share stories with them about how Diana helped people and they tell the children how much they would have loved their grandmother.''
This weekend, the royal will celebrate his 38th birthday, and it's believed his ''thoughts will be with'' Princess Diana.
Katie added to OK! magazine: ''William misses his mother. It must be emotional for him that she's not here to share this.
''She's still a significant part of his life so inevitably, on his birthday, his thoughts will be with her.''
William - who is the older brother of Prince Harry, and the son of Prince Charles - recently spoke about losing his mother during the BBC documentary 'Football, Prince William And Our Mental Health'.
The royal said raising children can be ''overwhelming'' at times, especially after having been through ''something traumatic''.
He explained: ''Having children is the biggest life-changing moment, it really is.
''And I agree with you, I think when you've been through something traumatic in life, and that is your dad not being around, my mother dying when I was younger, your emotions come back in leaps and bounds.
''Because it's a very different phase of life and there's no one there to help you.''