The new book titled Battle of Brothers: William and Harry – the Friendship and the Feuds, is by the author Robert Lacey. Mr Lacey said he will “address the unique and complex relationship at the heart of the royal family’s recent woes”.
The book is set to be released in October and will reportedly put the two royal brother’s relationship into a historical context.
It will allegedly examine how the “heir” and the “spare” dynamic has ran throughout history.
According to People magazine, the book’s synopsis reads: “Much reported on but little understood, Diana’s boys lived under constant scrutiny since birth.
“Raised to be the closest of brothers, the last 18 months has seen a devastating breakdown of their once unbreakable bond.
“With an unrivalled knowledge of court life and access to impeccable sources, Robert Lacey investigates the untold reality of the brothers’ relationship, explaining what happened when two sons were raised for vastly different futures and showing how the seeds of damage were sown as their parents’ marriage unravelled.”
The new book will also reportedly discuss how the siblings’ relationship has been affected by their wives Kate Middleton and Meghan Markle.
It also promises to address why Prince Harry and Meghan Markle decided to step back as senior royals earlier this year and move to LA with their son Archie.
Mr Lacey said he has been “astonished” by some of the revelations he has discovered while working on the project.
READ MORE: Prince Harry SNUB: Duke breaks ‘unwritten code’ to abandon William
Mr Lacey explained that his new book will provide readers with a glimpse inside the British monarchy.
He said: “These two brothers – once inseparable and now separated by much more than mere distance – have been acting out the contradictions that go back into their childhoods and even before that: into their parents’ ill-fated marriage.
“We have seen conflicts between heir and spare in every recent generation of the royal family – but nothing so profound as this.”
Mr Lacey’s book cover features an image from Prince Harry and Prince William’s public reunion earlier this year on Commonwealth Day.
Her Majesty The Queen led the congregation at the annual Commonwealth Day service at Westminster Abbey in early March.
During the meeting, the two brothers and their wives greeted each other before taking their seats.
A rift between the brothers reportedly emerged when Prince William warned Prince Harry against moving too fast in his relationship with Meghan Markle.
Last year, Prince Harry gave some insight into his relationship with his brother during an ITV documentary titled Harry & Meghan: An African Journey.
He said: “Inevitably stuff happens. But we’re brothers, we’ll always be brothers.
“We’re certainly on different paths at the moment.”