A new biography explores the parallels between the late Princess Margaret and Prince Harry, who have been in similar positions in the British royal family as well as in their love lives.

Royal biographer Andrew Morton, who just released his new book, "Elizabeth & Margaret: the Intimate World of the Windsor Sisters" about the relationship between Queen Elizabeth II and her late sister, notes that Princess Margaret sacrificed her love for duty, while Prince Harry chose his heart.

The late Princess was in love with Group Captain Peter Townsend, who served as an equerry to her father King George VI from 1944 to 1952 and held the same position for her sister Queen Elizabeth II from 1952 to 1953. However, as third-in-line to the throne at the time, she needed the approval of the Parliament and the Queen to marry, which she wasn't able to get as the then strict church rules did not allow the re-marriage of a divorced person with a living spouse.

After years of waiting for consent, the royal announced the end of her engagement with Townsend in October 1955. She said in a statement at the time: "I have been aware that, subject to my renouncing my rights of succession, it might have been possible for me to contract a civil marriage. But, mindful of the Church's teaching that Christian marriage is indissoluble, and conscious of my duty to the Commonwealth, I have resolved to put these considerations before any others."

"Margaret put duty before herself," Morton tells People magazine about the princess's decision. The author then compared it to Prince Harry's decision to quit as a senior member of the royal family for his wife Meghan Markle. Though Markle's divorced status didn't become a hurdle as the church has changed its rules, the couple has alleged unfair treatment by the palace and the British media.

"The wheel turns, 70 years later, and we have another couple having to make a decision: Do they put duty first or their own ambitions and desires first? And they put their own ambitions and desires first. That is the change we have witnessed during the Queen's reign," Morton said.

In his book, the biographer has pointed out that Margaret and Harry show similarities in terms of their relationship with their only siblings as well. "The parallels between William and Harry and Elizabeth and Margaret are there to be seen. In both cases you have one sibling who pushes boundaries, while the other is more cautious," Morton said.

Although the two pairs of siblings are separated by two generations, they have the same position in the British monarchy- "the heir and the spare."

"At one point, William and Harry were both part of the main branch of monarchy. Then William marries and has children, and his children take precedence. Whereas Harry is an ancillary branch in exactly the same way as Margaret," the author told the outlet about the royal "pecking order."

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Princess Margaret (L), Princess Elizabeth and Group Captain Peter Townsend gather June 13, 1951 in the Royal Box at Ascot Getty