Prince William is seething over his cancer-stricken dad, King Charles, having a private meeting with his estranged younger brother, Prince Harry — and now Harry is poised to become a part-time palace rep, insiders say.

The Duke of Sussex, 41, recently had tea with Charles, 76, at Clarence House in London for nearly an hour during a whirlwind four-day visit to his native England — more than five years after settling in California with his American wife, Duchess Meghan, per Daily Mail.

“It sickens William that Harry has wormed his way back into his father’s affections. To him, it’s just wrong on every level — and utterly ridiculous,” a source explains.

 <span class="wp-caption-text">James Whatling / MEGA</span>

James Whatling / MEGA

According to palace insiders, heir to the throne William, 43, lost the battle to permanently ice out his sibling, who with former Suits star Meghan, 44, ditched royal duties to cash in on their posh pedigrees with lucrative Hollywood deals and put down roots in a $14 million mansion in Montecito.

As Globe readers know, once in the States, the Sussexes gave several bridge-burning interviews bashing Harry’s kin, which appeared to erase the prince’s chances of being welcomed back into the royal fold. But the sentimental king seems to have softened his stance in the 20 months since receiving his diagnosis of an undisclosed form of cancer, which is said to be incurable.

“The fact Harry now has this direct line back to the family — despite all the pain and misery he’s inflicted — simply defies belief. William is totally bewildered and frustrated that it’s being sanctioned,” the source shares. “It totally changes royal history.”

“William’s big point is that there’s no evidence to suggest Harry has changed. He’s convinced this groveling effort is part of an overall plot for the Sussexes to hold on to their precious titles and try to salvage what they can from the monarchy, while his father’s still alive to be manipulated.”

 <span class="wp-caption-text">MEGA</span>

MEGA

Sources say Harry was thwarted by the late Queen Elizabeth in his initial attempt to split his time between the U.K. and California when he and Meghan expressed their desire to step back from being full-time royals.

After that, Meghan implied in an explosive 2021 TV interview that some of her in-laws were racist for speculating about their unborn son’s skin color and also accused them of turning a blind eye toward her mental health struggles.

Sources say Charles and William’s peace-keeping wife, Kate, Princess of Wales, want to welcome back Harry, but his brother refuses to choose blood over duty.

 <span class="wp-caption-text">James Whatling / MEGA</span>

James Whatling / MEGA

The insider shares, “The king and others — Kate included — are urging William to show mercy and give peace a chance, but he’s saying that’ll happen when hell freezes over.”

“Harry may have wormed his way back into Charles’ heart, but it’s going to take a lot more to prove to William that he’s changed.”

Since the successful peace talks with his father, Harry seems to have a spring in his step and crowed that he’s “closer” to bringing his kids — Prince Archie, 6, and Princess Lilibet, 4 — to England.

 <span class="wp-caption-text">Archwell</span>

Archwell

He also defiantly claimed his “conscience is clear” and he didn’t “air dirty laundry” by dishing about his life and family on TV and in his scathing memoir, Spare, according to The Guardian.

But according to another insider, worried Meghan is being driven to tears over fears that her homesick hubby is being sucked back in by the royals — and that they could poison him against her as he rebuilds his relationship with the monarchy.

“Harry’s insisting there’s nothing to be nervous about. That this is a wonderful thing for the whole family, and that soon enough they’ll be dining at Buckingham Palace and enjoying all the fruits that come with being a royal, while still doing things their own way as far as service and career,” the insider confides.

“But Meghan’s not so sure. She’s still deeply suspicious that the royals are trying to divide and conquer them as a couple. She’s in a very vulnerable position right now.”