Prince Harry will reportedly unleash his sense of “bitterness” at having to play “second fiddle” to William in his new memoir.
Senior royals are believed to be bracing themselves for new revelations from the Duke of Sussex in his book called Spare, which is due to be published on January 10.
And Harry is expected to go into greater detail about his relationship with William than he did in the recent Netflix series by the Sussexes.
Harry accused his brother of "screaming and shouting" at him in the documentary while Meghan described the royals as acting formal even behind-the-scenes. They portrayed the royals as tone-deaf and uncaring about their emotional states.
The new book will look at the Royal Family from the eyes of the Duke of Sussex and the way he feels frustrated at being “spare” with the attention on William as heir to the throne.
While at the same time the King will not be the focus of Harry’s attention and he is likely to escape from the majority of the criticism.
“At the heart of this book lies a sibling rivalry between little brother and big brother," a source told The Sun.
"It will reveal Harry’s bitterness and feelings of unfairness that by the nature of hierarchy and birthright that he always played second fiddle to older William.
“The falling out is to be covered in the book in detail and what aggravates is it’s not an outsider revealing these private moments — it’s Harry giving his one-sided account of family affairs.
“Harry and William were meant to stick together and support each other.
"Their mother Diana always warned them they must never fall out because they would need one another. It is very sad it’s reached this stage.”
Harry will rake in more than £36million for lifting the lid on his time as a royal leading up to his acrimonious exit from “The Firm” with wife Meghan.
The 416-page memoir, ghost written by American novelist J.R. Moehringer and complete with a striking cover image of Harry, will contain “raw, unflinching honesty”, according to the publishers.
The book was set to come out this autumn but the date was pushed back as a mark of respect following the death of the Queen.