The royal biographer told Vanity Fair: “When you compare personalities, Harry is like Margaret, a royal rebel.
“Margaret once said ‘disobedience is my joy’ and you see some of that in Harry.
“The Queen also knew Margaret sometimes felt like an outsider and I think that’s why she has made sure the door is always open for Harry to return to the royal fold.
“She will have a lot of empathy and sympathy for him because she grew up watching her younger sister act the role of the spare, which is not easy.”
The author of new book Elizabeth & Margaret claimed that a big difference between Harry and Margaret is that the Queen’s late sister was “always loyal to the crown”.
He said: “The Royal Family is a hierarchy and if you’re not number one that can be challenging.
“There are also many parallels between the relationship between Elizabeth and Margaret and William and Harry.
The Duke and Duchess of Sussex plunged the Royal Family into crisis with their controversial Oprah Winfrey interview, which aired last month.
The ex-Suits star and the Queen’s grandson made a set of bombshell claims about the monarchy in the TV interview, including accusations of racism.
The royals made clear they did not agree with all of Meghan and Harry’s version of events, saying in a statement how “some recollections may vary”.
Royal author Penny Junor accused the Sussexes of betraying the Royal Family in the year since Megxit.
Ms Junor said: “When Harry and Meghan left a year ago people were surprised and disappointed because they were a great pair.
“Harry was a hugely popular royal and Meghan was a great asset to the family.
“A year on, I think a lot of people are really angry and think that they have betrayed their family and lobbed a huge bomb into the heart of the institution and sort of taken a swipe at the UK as well.”