TORONTO -- The Duke of Cambridge has revealed that the "life-changing" experience of having children brought back the emotions he felt following the death of his mother, Princess Diana.

In a new BBC documentary, Prince William opened up about how having children is "one of the most amazing moments in life, but also one of the scariest" when having lost one鈥檚 own parent.

"I think when you鈥檝e been through something traumatic in life -- and that is like you say 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," William said. "And there's no one there to, kind of, help you, and I definitely found it very, at times, overwhelming."

William was speaking to former professional footballer Marvin Sordell for the forthcoming documentary that examines men's mental health through the lens of football.

Sordell described becoming a parent as "the hardest time" in his life as he did not grow up with a father.

"Having children is the biggest life-changing moment, it really is," William responded.

William said he and his wife Catherine, the Duchess of Cambridge, rely on one another for support when they experience those "overwhelming" feelings. They have three young children together -- Prince George, Princess Charlotte and Prince Louis.

"Me and Catherine particularly, we support each other and we go through those moments together and we kind of evolve and learn together. But I think emotionally things come out of the blue that you don鈥檛 ever expect, or maybe you think you have dealt with," William said.

William took part in a similar film released last year in which he called the loss of his mother a "pain like no other."

William was 15 and his brother, Prince Harry, was 12 when their mother died in a Paris car crash in 1997. In recent years, William and Harry have talked extensively about how they dealt with their mother鈥檚 death through their Heads Together mental health campaign.

The new documentary, titled 'Football, Prince William and our Mental Health,' is expected to air May 28 on BBC One.