Prince William, Prince Harry on mom Diana's death: 'We are uniquely bonded'

April 21 (UPI) -- Prince William and Prince Harry say they became "uniquely bonded" after their mom's death.

The British royals discussed losing mom Princess Diana with William's wife, Kate Middleton, Duchess of Cambridge, in a video for a new Heads Together campaign promoting mental health.

"We have been brought closer as a result of the circumstances," Prince William said of his mom's death. "You are uniquely bonded because of what we've been through. Even Harry and I though, over the years, have not talked enough about our mother."

"I always thought to myself, 'Whats the point of bringing up the past? What's the point in bringing up something that's only going to make you sad? It ain't going to change it,'" Prince Harry explained. "When you start thinking like that, it can be really damaging."

"What happened with us, and must happen with others as well, is you have to prioritize your mental health," Prince William advised. "Someone has to take the lead and has to be brave enough to force that conversation."

Heads Together works with young people, emergency response, homeless charities and veterans to promote mental wellbeing and end the stigma around mental illness. The new campaign, "#OktoSay," encourages people to open up about emotional challenges.

"That's part of the healing process and it's part of sharing your problems, to half them and to make them better with someone you trust and someone you know is going to help you," Prince William said.

"We've never really talked about losing a mum at such a young age, and then you speak to other families and little kids and stuff, and you think, 'Wow, I don't want them to have to go through the same things,'" Prince Harry added. "You want to help as much as you can and try and empower them to have that conversation."

Prince William and Prince Harry were 15 and 12, respectively, when Princess Diana died at age 36 in 1997. Prince Harry told the Telegraph this month that he sought counseling four years ago after "shutting down" his emotions for years after his mom's death.