Royal insiders said it was likely a “nice surprise” for the King, who hadn’t heard from Harry, either by phone or message, “for some time”.
The King is understood to have had a friendly chat with his son during this transatlantic call.
Charles also received a video of Archie, four, and Princess Lilibet, two, singing happy birthday to their grandad, who they’ve only met a few times.
Insiders say that Charles feels no pressure with Harry and despite their differences, they “still have that father-son bond”.
He also reportedly sees his late ex-wife Princess Diana’s “good qualities” in his son.
A source told Closer: “Charles doesn’t feel pressure when talking to Harry, unlike William, who is itching to be king.
“They’ve had their differences, but still have that father-son bond. That’s how they mended things.”
“Charles has clarity with age, and if he wants anything, it is for William and Harry to repair their relationship,” said another insider.
“He’s telling William to be the first one to reach out and be the bigger person. It’s his mission to get the boys on good terms.”
The source also mentioned that Harry wanted “to start the new year off right and focus on making amends” with Charles.
They added: “And lucky for him, Charles wants that, too.”
