Prince Harry's memoir will be especially tough on Prince William and worse for the royal family than they expect, report says

• Prince Harry's tell-all memoir "Spare" will be published on January 10.
• The book will be worse for the royal family than they expect, The Sunday Times source said.

Prince Harry's upcoming memoir will be especially tough on his brother, Prince William, and relatively forgiving of King Charles III, according to The Sunday Times.

Citing a source with knowledge of "Spare," which will be published on January 10, The Sunday Times reported that the ghostwritten book is so tough on William that the brothers might struggle to ever repair their relationship.

The source, who was not named, told the newspaper the book would be worse for them than the royal family expected.

"Everything is laid bare. Charles comes out of it better than I had expected, but it's tough on William, in particular, and even Kate gets a bit of a broadside.

There are these minute details, and a description of the fight between the brothers. I personally can't see how Harry and William will be able to reconcile after this."

In the "Harry & Meghan" Netflix series released last month, Harry accused his brother's staff of trading stories with the press about him and Meghan Markle. Harry also mourned his damaged relationship with William, Insider previously reported.

The Sunday Times reported this month that Prince William has cut all contact with Harry over the Netflix series and has no plans to speak with him again.

The upcoming memoir also touches upon Harry's grief over the death of his mother, the late Princess Diana.

"The overall impression is that this is a man who has never recovered from the trauma of his mother dying so young, and then along comes Meghan, and he projects on to her a parallel with Diana," The Sunday Times source said.

The book, ghostwritten by American writer JR Moeringer, is described by publisher Penguin Random House as a "landmark" publication that is an "honest and captivating personal portrait."

Harry said in a statement published by Penguin Random House: "I'm deeply grateful for the opportunity to share what I've learned over the course of my life so far and excited for people to read a firsthand account of my life that's accurate and wholly truthful."