With royal fans still recovering from the release of Finding Freedom, another biography is expected to include some candid insights into the Royal Family’s inner workings. The book Battle of Brothers: William, Harry, and the Inside Story of a Family in Tumult centers on the Dukes of Cambridge and Sussex’s heavily scrutinized relationship.

Princes William and Harry have had to overcome several challenges in their lives as a result of growing up in the spotlight and dealing with the pain of their mother’s sudden death. And the brothers have chosen very separate directions, with William mostly adhering to royal protocol in the hopes of one day becoming king, while Harry has left royal life behind for a new life in the United States with the Duchess of Sussex.

When it comes to Prince Harry’s relationship with his older brother, Prince William, things are confusing. ET spoke with royal historian Robert Lacey regarding his new book, Battle of Brothers, which details Harry and Will’s childhood relationship and eventual rivalry, and he discussed all of the complicated factors at stake.

According to Lacey, William and Harry didn’t always enjoy the same reputations as they do today, with William being the more serious of the two and Harry being the more defiant of the two.

Lacey tells ET’s Nischelle Turner, “One of the objectives of the book is to go back into the past of these two boys, into their childhoods, to see the way in which their lives were shaped, cruelly really, by the breakdown of their parents’ marriage and by the royal roles and distortion that was placed upon them,” “You know, I describe how when they were born, it was William who was the rambunctious character and it was Harry who was the good little boy who sucked his thumb. Then William discovers that he’s going to be king, he becomes much more serious and quiet between the age of six or seven. Harry goes the other way .”

While the friction between the two brothers existed even before Harry’s tumultuous affair with Meghan Markle, according to Lacey, it was intensified by her arrival.

“I talked to Ken Wolf, who was the bodyguard to Harry and William when they were little boys,” Lacey said. “And he said how William was always sort of jealous of the lovable rogue reputation that Harry had and the affection that he generated. And there is certainly a school of thought that William and [his wife] Kate were not happy at the way in which these royal rock stars, Harry and Meghan, overshadowed them, and that they’re quite happy now to have seen them out of the country.”

“There is a school of thought that it suits William very well for Harry and Meghan to be the scapegoats living abroad,” Lacey added.

Lacey recalled William being “very protective” of Harry during the brothers’ youth. “He’d had the same impulse towards his mother as things got bad for her. His was the shoulder that she cried on. But there’s a sense also of course that this robbed him of his youth and I think the responsibility he had for Harry also robbed him of the, you know, carefree nature of his childhood. That is why we are told he—until last year—he certainly hadn’t told his own son, Prince George, that he was going to be king one day. William felt that that was something that’d been a burden too much for him as a child and he didn’t want that for his own son.”

Robert Lacey claims that the Cambridges were delighted to see Meghan and Harry depart the UK after they chose to step down from senior royal duties in order to live a “financially independent life”

He said that the rift between William and Harry was “getting worse” particularly now that they reside on opposite sides of the world.

“That’s one of the reasons people close to the scene doubt whether there’ll be a reconciliation because you know it’s the old syndrome – this town is too small for both of us.”

He continued, “So first of all it’s called battle of brothers, and you say that this feud between William and Harry is worse than people thought.

“I think every day makes it clear that it’s worse.”

Mr Lacey, on the other hand, claims that the enmity between the two dates back further, claiming that Harry was painted as a “court jester” sort owing to his crazy drinking days in his youth.

“I would say that there were stresses and strains there before and then with the advent of Meghan, that was what provoked the really big break,” Lacey says. “William, from all the turmoil of their childhood, took strength from the idea of his duty and what lay ahead for him as king… Harry caught onto the importance of love. So, when he found Meghan, he went for that, and when William said to him, ‘Look, perhaps you should slow down a bit,’ Harry exploded. William then went to his uncle, Charles — who is Diana’s brother who had been a sort of godfather to the boys — and asked him to intervene and suggest to Harry that he slow down. And Harry rejected William’s model. He knew what he wanted, he loved this woman, and he was going to marry her so that was certainly the beginning of the rift.”

Both brothers, according to Lacey, have a temper, which could confuse some who believe William is far more even-keeled.

He states, “There are numerous occasions when in recent times the two brothers have lost their temper with each other — it’s been quite well known that Harry has a volatile temper,” “As I started writing the book, a lot of people close to the scene would say, ‘Well, you know that William has a temper as well.’ He would get angry with his father, Charles, when he didn’t feel that Charles was doing the right thing as a future king. We know this because [Prince Charles’ wife], Camilla, was shocked when she sometimes found William upgrading and insulting his father. She talked about it to family and friends — that’s how I found out about it .”

Lacey points out that the coronavirus outbreak has hampered the brothers’ efforts to mend their relationship.

“When [Harry and Meghan] left in March, they were committed to coming back in the summer for the queen’s birthday and all the celebrations that go with that,” he says. “They were committed to coming back in the autumn for various military occasions that meant a lot to Harry and that has not been possible, so it may well be when and if life gets back to normal, the brothers can spend more time together and these fences could be mended.”

“In Britain, we all hope there will be some sort of coming together that will require compromise on both sides,” he adds. “The alternative is that they decide… that as brothers, we’re going to go our own separate ways,” he also says. “Next July the 1st, both brothers have promised to be in Kensington Palace gardens to celebrate the 16th anniversary of their mother’s death with a statue they have commissioned to Diana. They are going to be there … Prince Charles is going to be there, presumably, presumably Camila will not be there and the world will be looking at them and the world will want to know.”

Lacey was skeptical when asked whether William and Harry would ever reunite in a royal role. “I think we’re gonna have to face the reality that these are two brothers that have drawn two different lessons from their troubled childhoods and they’re going in different directions,” he said. “I think the best we can hope for is that they can maintain their fundamental love and respect for each other and remain [on] good terms for the future.”