Prince Harry, 33, said he “let everything around me tear me to pieces” as he struggled to come to terms with the loss of his mother, Princess Diana.
Journalist and author Angela Levin said the prince’s vulnerable side means his wife, the Duchess of Sussex, feels like she has to protect him.
In ‘Harry: Conversations with the Prince, seen by Express.co.uk, Ms Levin said: “Unlike William, Harry needs lost of reassurance and understanding.
“Even today he sometimes has an air of vulnerability and sadness.
“It’s part of what has endeared him to so many people of all ages and types around the world and perhaps why Meghan Markle sometimes feels the need to be motherly towards him.”
Prince Harry told how for years he tried to hide his feelings about the loss of Princess Diana.
The prince was just 12 when his beloved mother was torn from him after she was killed in a car crash in a tunnel in Paris in 1997.
Ms Levin said: “For years he had hidden his concerns in public. ‘I was a typical twenty, twenty-five, twenty-eight-year-old running around going ‘life is great’, ‘life is fine’.
Meghan Markle sometimes feels the need to be motherly towards Prince Harry
“He could help other people, but not himself.
“For years Harry felt he was ‘very close to a complete breakdown on numerous occasions’.
“He knew something was wrong, but he said: ‘I just couldn’t put my finger on it. Instead of dealing with it I buried my head in the sand and let everything around me tear me to pieces.’”
But it was his older brother, William, who Harry eventually opened up to and persuaded him to seek help.
Prince Harry said he was ‘close to a breakdown’ following the death of his mum Princess Diana
Meghan Markle has been supporting Prince Harry since the death of this mum
Harry said: “I started to have conversations and actually all of a sudden this grief that I have never processed started to come to the forefront and I was like, there is actually a lo of stuff here that I need to deal with.
“For me personally, my brother, you know, bless him, was a huge support to me. He kept saying ‘This is not right, this is not normal, you need to talk to someone about stuff, it’s OK.’
But it was a few years before the Duke of Sussex found the strength to seek help for his mental health problems.
The 33-year-old told Ms Levin: “The timing wasn’t right. You need to feel it in yourself, you need to find the right person to talk to, as well.”
Prince Harry has continued his mother’s legacy, raising awareness over Aids and homelessness issues, not only in the UK but around the world.
He along with his brother William, sister-in-law Kate and wife Meghan, are patrons to mental health charity, Heads Together.