Why Prince William Is Still 'Incredibly Upset' Over Prince Harry: Royal Expert (Exclusive)

'There hasn't been any contact between them for some time,' royal expert Katie Nicholl tells ET.

Prince William and Prince Harry's relationship is still fraught. Royal expert Katie Nicholl tells ET that the brothers haven't spoken "for a long time" following the January release of Harry's memoirSpare.

"My royal sources say that any chance of a reconciliation really isn't ruled out, but it's certainly not going to happen anytime soon," Nicholl says. "Prince William is still incredibly upset with Harry's autobiography, which, of course, really cast William in a pretty bad light. No one's going to forget anytime soon the stories of them coming to physical blows, and William allegedly shoving Prince Harry, forcing him onto the ground where he landed onto a dog bowl."

Nicholl adds of the brothers, "They don't talk. There hasn't been any contact between them for some time now is my understanding."

"I'm told by several sources close to the Prince of Wales that William really just cannot find it in his heart at the moment to forgive his brother for what he's done," she notes. "I think Kate, Princess of Wales, she's always always had a very close relationship with Prince Harry, but she's been left quite devastated by some of the anecdotes that Harry told in Spare that didn't cast her in a particularly good light. I think there's a great sense of betrayal."

As such, Harry isn't expected to see William during his brief visit to the U.K. for the WellChild Awards, with Nicholl telling ET, "Any chance the brothers seeing each other, I'm told, is simply not on the cards."

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Likewise, Harry is not expected to see his father, King Charles III, while in the U.K.

"The king is still in residence at Balmoral. That's where he will stay over the coming days. Apparently, there is no time in his schedule for him to see Harry," Nicholl says. "... There are no plans that we are aware of for Harry to visit the king, and we're told the king's diary is pretty busy at the moment, too."

Harry's "fleeting" 48-hour trip simply doesn't leave "much time for any family reconciliation," according to Nicholl.

"I think the fact that there isn't any family reunion really gives us quite an indication as to the state of the relationship both between Prince Harry and his father and with his brother," she says. "I'm told... there haven't been any conversations [with William] for a long time. There is some communication with Charles, but very little."

The little communication Harry has had with Charles, Nicholl says, is also due to the contents of Spare.

"There has been so much criticism leveled at the royal family, really personal criticism leveled at Camilla, the Queen in his autobiography," she explains. "I think really that was very below the belt as far as the king was concerned. I think that has really damaged Harry's relationship with Charles."

"I understand from sources close to Charles that he wants to have a relationship with his son," Nicholl continues. "They do speak, but it's very occasional. But I think the fact that they are not seeing each other on this trip... I think it's a clear indication that the relationship is certainly strained between father and son."

That strain is worsened by the "mater of trust," Nicholl explains.

"Charles, I think, is more keen for some sort of reconciliation. He'd like to have a sit-down and talk with his son, but there is a genuine concern on the king's part that anything he says could then be sort of retold via Harry to a news media outlet, because that's what's happened in the past," she says. "I think there is a real trust issue at stake here."

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After Harry attends the WellChild Awards on Thursday and marks the one-year anniversary of Queen Elizabeth II's death on Friday, he'll fly to Düsseldorf, Germany, for the start of the 2023 Invictus Games on Sept. 9. Harry's wife, Meghan Markle, will join him for the latter portion of his trip.

"The Duke and Duchess of Sussex are delighted to be attending the Invictus Games 2023 in Düsseldorf," a spokesperson for the couple previously told ET. "The duke will be in attendance and will be joined by the duchess at a later date. Together they will remain in Düsseldorf until the end of the games."