According to the Times, the Princes decided not to attend the royal tea with the Queen, 92, and Trump, 71, and his wife Melania, 47,at Windsor Castle in England on Friday, July 13.
"The royal father and son apparently shared their desire to not take part in the arrangements during informal discussions regarding the president's four-day tour," the British publication reported.
Although Trump's trip wasn't considered a state visit, top politicians usually expect to see more royal family members besides the Queen.
An insider told the Times flatly, "This business of Prince Charles and Prince William not being there for the Trump visit was a snub."
They simply "refused to attend," the source said.
"It's a very, very unusual thing for the Queen to be there on her own. Usually she is accompanied by somebody," the royal insider noted.
While President Trump is controversial, many consider it bizarre that the Queen's son Prince Charles, 69, the heir to the throne, wouldn't attend the meeting, if only to honor the long relationship between Great Britain and the United States.
The source shrugged of Charles, "He goes to what he wants to go to, and if he had wanted to be there he could have been."
Instead, while Trump was in town, Prince Charles attended a board meeting for his company AG Carrick at Highgrove as well as an event with Gloucestershire police.
His son, Prince William, aka The Duke of Cambridge, took part in a charity polo match.
A royal official involved in making the arrangements for Trump's visit admitted to the Times that Trump's time with the Queen was "kept to the bare minimum."
Determined Elizabeth, who reportedly has refused knee surgery because she doesn't want to miss any official engagements, met President Trump and FLOTUS wearing a smile and a bright blue outfit with matching hat on Friday.
Critics sniffed that Trump was late to the tea and also turned his back on the Queen to inspect the guard of honor, a big protocol no-no.
But the royals have shown favoritism in the past as in 2016, President Barack Obama and wife Michelle met much of the family!
The Obamas socialized with Queen, her husband Prince Philip, now 97, Prince William, 36, his wife Kate Middleton, 36, and Prince Harry, 33.
Last year, former President Obama hung out with Harry at the Invictus Games as they've had a "bromance" going for some time. Markle, 37, didn't join them.
Ideas about President Trump meeting the younger royals during his just-completed trip to England were ignored, the paper reported.
However, a Downing Street source told the Times, "This was always going to be just the Queen."
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