TORONTO -- The apparently fractured relationship between royal brothers Prince William and Prince Harry may have been baked into their bloodline, according to a prominent British biographer.

In an interview set to air Nov. 21 on CTV鈥檚 Pop Life, Robert Lacey, author of 鈥淏attle of Brothers,鈥 noted a long history of sibling rivalry in the Royal Family.

Some have suggested that 鈥渢he heir and the spare鈥 way of thinking -- that William was groomed to be king and Harry played second fiddle -- affected how they were raised and even Harry鈥檚 eventual divergence from the family. Similarly strained were the relationships between Queen Elizabeth and Princess Margaret, and between Prince Andrew and Prince Charles.

鈥淗arry is in fact the third spare that this has happened to. All the spares in the Queen鈥檚 reign have come to grief,鈥 said Lacey. 鈥淭hey start off as costars.鈥

Lacey said the 鈥渞ather cruel stereotyping鈥 of birth order in the Royal Family w鈥媋s a 鈥渕ajor factor鈥 in the brothers鈥 relationship, the consequences of which may have played a role in apparent feuds in recent years, namely Harry pulling away from royal duties to move to North America with Meghan, the Duchess of Sussex. In a 2019 interview before the major announcement that he would step back, Prince Harry addressed rumours of a feud between the brothers, saying:

鈥淲e鈥檒l always be brothers. We鈥檙e certainly on different paths at the moment, but I will always be there for him and, as I know, he will always be there for me.鈥 William never publicly reciprocated the olive branch, said Lacey.

For royal watchers like Lacey, who is a historical consultant to the Netflix series The Crown, the forking of the brothers鈥 lives began at a young age and was forged by the dissolution of their parents鈥 marriage and mother鈥檚 death, a timeline detailed in Lacey鈥檚 book, which was . Lacey recounted a scene in which a four-year-old Harry told his nanny that he didn鈥檛 need to 鈥渂ehave, because he wasn鈥檛 going to be king like his then-six-year-old brother William, who at that time was already becoming more serious, preparing for his royal destiny.

鈥淚 would go so far as to say that the knowledge he was going to be king kept William going through all the trials and tribulations of the breakdown of his parents' marriage, not to mention the death of his mother,鈥 said Lacey.

鈥淔or Harry, he took a different lesson from what had gone wrong. Love is what matters to him. And so we have this classic clash that goes right back to 1936 in the British monarchy -- a clash between love and duty. And just as in '36, the abdication of Edward VIII, duty won, love was exiled. The same has happened now.鈥

Earlier this year, Harry and Meghan moved to Canada and later California, where they struck a content deal with Netflix and where they reportedly plan to spend most of their time. As in other times throughout the Royal Family鈥檚 history, the turbulence of recent has led many to wonder: will the monarchy survive this? Lacey is certain it will, though it鈥檚 unclear how the public will respond to an eventual King Charles III and a Queen Camilla. 

鈥淭he Royal Family will come back,鈥 he said. 鈥淐anadians must speak for themselves, but I'm sure so long as Elizabeth remains Queen, people鈥檚 loyalty to the monarchy will remain.鈥