"The younger-sibling syndrome is an enduring problem," author Robert Lacey said of how siblings fit in the royal system

The struggle is real for younger siblings of the future monarch.

More than a half century before Prince Harry’s shocking royal exit, his great-aunt Princess Margaret struggled with her place in the shadow of her older sister Elizabeth.

“The younger-sibling syndrome is an enduring problem,” Robert Lacey, author of the books Majesty and Monarch, tells PEOPLE in this week’s cover story. “The system has not found a way of giving them the recognition that they need.”

And as the older sibling has children, the problem only worsens.

“Until Elizabeth produced heirs, Margaret was a possible future Queen,” added Lacey. “It is a family situation of conflict that goes back over generations.”

Before 1936, neither Elizabeth nor Margaret expected their father to become king. But when his brother, King Edward VIII, abdicated the throne to marry American divorcée Wallis Simpson, their lives were turned upside down.

Princess Margaret, Prince Harry
Princess Margaret and Prince Harry
| Credit: Hulton Archive/Getty Images; EAMONN M. MCCORMACK/Getty Images

About five years after becoming Queen, Elizabeth and Margaret’s relationship was tested by Margaret’s love affair with Peter Townsend, whom she wanted to marry.

The Queen asked them to wait, and according to Margaret’s biographer, Christopher Warwick, the relationship fizzled out.

Britain's Queen Elizabeth (R) waits on the steps of St. Paul's Cathedral with her grandsons Prince Harry (L), Prince William (2nd L) and Princess Margaret (2nd R) after attending a national service of thanksgiving in celebration of The Queen Mother's forthcoming 100th birthday in London 11 July 2000
Prince Harry, Prince William, Princess Margaret and Queen Elizabeth, July 2000
| Credit: ADRIAN DENNIS/AFP via Getty

Margaret — who died in February 2002, just one month before their mother’s passing — is portrayed by actress Helena Bonham Carter on Netflix’s The Crown, which chronicles the Princess’ rollercoaster love life.

A similar rift between brothers Prince Harry and Prince William can be traced back to the early days of Harry and Meghan Markle’s romance, when, sources said, William cautioned Harry about moving too fast.

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Prince Harry Meghan Markle People Magazine Cover
PEOPLE Cover, Jan. 27, 2020

Last week, Meghan and Harry announced their historic decision to step down as senior royals, as the couple felt increasingly ostracized from the family.

In their statement, the Duke and Duchess of Sussex said they wanted to “carve out a progressive new role within this institution” — however, the public announcement came with little formal warning and left senior royals “hurt,” something that was “so avoidable,” a royal source said.

A family friend told PEOPLE that the couple felt they had no choice but to manage things the way they did, even as they went against the family’s “never complain, never explain” mantra.

“This is not how they wanted to handle this, but Meghan and Harry’s hand was forced,” said the friend. “There is so much bad blood in that family — it’s toxic.”