Carole Middleton has reportedly acted like a "second mum" to Prince William after his wedding to her daughter Kate Middleton in 2011.

Royal biographer Angela Levin told The Sun's magazine Fabulous that Carole taught her son-in-law "how a loving and supportive family works" and provided him a "real sense of normality amid any chaos." The Duke of Cambridge, who lost his mother Princess Diana in a car crash when he was just 15, had a "dysfunctional family background" that gave him "barely a clue of what a normal family life was like," Levin said.

"William adored Diana and was drawn to her magnetic charm, but she was relentlessly demanding on him as a young child, describing him as her 'closest confidant' and talking about her lovers, when it's a mother's duty to care for her son, not the other way round," the royal expert said about the Princess of Wales.

Levin added that contrary to Diana, "Carole relieved William of such burdens by accepting him for who he was rather than what he was."

"She made him feel secure, comfortable and protected and he didn't have to worry about what he said or be responsible for her emotions," Levin said.

She also said that William's close relationship with his mother-in-law is one of the key differences between him and his younger brother Harry, who has openly spoken about dealing with mental issues after losing his mother at the age of 12.

"Children of broken homes, especially if the parental break up was unpleasant, often don't know how a good relationship works. William learnt through the Middletons how a loving and supportive family works. It has been the bedrock of making Kate loving, calm and confident. Harry hasn't had that parental opportunity," Levin explained.

While William has previously said that he loves his in-laws Carole, Michael, James, and Pippa Middleton, the only member from Meghan Markle's family with whom Harry has a relationship is his mother-in-law, Doria Ragland. The Duke of Sussex has never met his father-in-law Thomas Markle, whose feud with his daughter is very much public.

Levin said that Harry's "background has just been of bitter fighting and incompatibility." She continued: "Both he and Meghan come from very damaged backgrounds and must carry with them some of the negativity. It must be hard for them to help each other and lack experience in how stable, strong, understanding relationships work."

29 April 2011: Prince William and Kate Middleton pose in the Throne Room at Buckingham Palace with members of their families after their wedding. Front row: Grace van Cutsem, Eliza Lopes, Prince Philip, the Queen, Margarita Armstrong-Jones, Louise Windsor, William Lowther-Pinkerton. Back Row: Tom Pettifer, Camilla, Prince Charles, Prince Harry, Michael Middleton, Carole Middleton, James Middleton and Philippa Middleton AFP