While many Britons might disagree with the decision of Prince Harry to lead a different life in the United States, his grandmother, Queen Elizabeth, could be his most sympathetic ally.

Royal biographer Andrew Morton believes that Queen Elizabeth is very patient with Harry, despite his recent actions against the monarchy because she understands how hard it is to be the spare. The queen apparently sees many similarities between Harry and her beloved younger sister Princess Margaret.

According to Morton, the queen has learned, through her experiences with Margaret, that shutting out a "lost soul" would only worsen the situation. So, she is more accommodating and willing to stand by her grandson even during his most embarrassing mistakes.

The biographer said that like Margaret, Harry has been a disobedient "royal rebel" who also had problems finding his place in the monarchy. Morton said that this could be why Queen Elizabeth continues to keep the door open for Harry's return.

As children, both Prince William and Harry, as the heir and the spare, were part of the main branch that would be directly in line to the British throne. However, as William had children with Kate Middleton, Harry's ranking changed and he became the auxiliary branch.

This was the same way with Margaret's status when the queen gave birth to four children. Margaret's line in the throne became the auxiliary branch and her children, David Armstrong-Jones and Sarah Chatto (nee Armstrong-Jones), were pushed further in the line of succession as Queen Elizabeth's own branch of the family expanded and the dynamics shifted.

Margaret was also torn between love and duty in her younger years and this caused a friction between her and the queen. But as she got older, the spare decided to put her "duty before herself" and served the Crown until she became sick and died in 2002. Morton said that this was the big difference between Margaret and Harry as the queen's sister was "always loyal to the crown" and sacrificed her own happiness in the name of duty.

Morton details the complex relationship of Queen Elizabeth and her only sibling in the new book Elizabeth & Margaret: The Intimate World of the Windsor Sisters. Incidentally, the biographer confirmed that he is currently a consultant in The Crown season 5, which will tackle another complex relationship between Queen Elizabeth and Princess Diana. The biographer was a close confidant of the Princess of Wales who wrote her bestselling authorized biography.