The sisters are reportedly stunned over the news of the book deal with a senior royal source telling the Mail Online:"The emotional turmoil as they wait over a year for publication is going to be torturous. What's really telling is even the relatives he remains closest to, like Princesses Eugenie and Beatrice, are stunned by what he's up to."
"Let’s be honest, Harry has never been close to the Duchess of Cornwall," they added. "If he documents their fraught relationship in the book it could be very damaging at a time when Charles is laying the groundwork for her to become Queen."
Ingrid Seward, editor-in-chief of Majesty Magazine, told The Express that Prince William will likely be the most impacted by the book.
"William is probably the one that will come out of this worst of all because there is a row between William and Harry and basically if Harry says things that are inappropriate about the monarchy, that is William’s future," she said.
"It’s not Harry’s future, he is out of it now, but it is William’s future."
She added Charles will be heavily affected: "It is his son and how hurtful can it be for him to hear Harry say that his father hasn’t been a great father - which is more or less some of the things he has already said."
Prince Harry announced his "wholly truthful" memoir last week, promising to be a "first-hand" account of his life so far.
In a statement, the 36-year-old said: "I'm writing this not as the prince I was born but as the man I have become.
"I've worn many hats over the years, both literally and figuratively, and my hope that in telling my story - the highs and lows, the mistakes, the lessons learned - I can help show that no matter where we come from, we have more in common than we think.
"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 first-hand account of my life that's accurate and wholly truthful."
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