A former High Court judge has said that Prince Harry's mental health issues may have been exacerbated by the breakdown of his parents' marriage.
Sir Paul Coleridge claimed that "had his family been united at the time of his mother's death it is likely that Harry would have coped better".
He also suggested that their father's new relationship might have made his problems worse.
Earlier this week Prince Harry, now 32, said that he had sought counselling in his late twenties to help him come to terms with the death of his mother, Diana, Princess of Wales.
He said he had been "very close to a complete breakdown on numerous occasions" and had struggled with aggression, which he had dealt with by seeing a therapist and taking up boxing.
His parents divorced in 1996 after 15 years of marriage. Diana, Princess of Wales was killed in a car accident a year later, when Prince Harry was 12.
His father, the Prince of Wales, married Camilla Parker-Bowles, now the Duchess of Cornwall, in 2005.
In a letter to The Times, Sir Paul called Prince Harry's disclosures, made to The Daily Telegraph earlier this week, "brave, poignant and timely".
He added: "The divorce of his parents and the break-up of his family, followed by the death of his mother, can only have compounded his insecurity.
"Recent US research has highlighted the extra trauma caused to children at the time of family breakdown by the introduction of a new parental partner.
"Both the princes had to endure this, too. And to make matters worse it all took place in the glare of publicity."
Sir Paul, who worked in the family division of the High Court, retired in 2014 and is now chairman of the Marriage Foundation, which campaigns against family breakdown.
In his letter he added that "unless and until we acknowledge that family instability and family breakdown is the biggest driver of mental health problems in children and young people, we will never get on top of the problem.
"All other remedies are merely sticking plasters."
A spokesman for Kensington Palace declined to comment.