The royals fear that Prince Harry and Meghan Markle could "hijack and overshadow" the Queen's upcoming Platinum Jubilee celebration.
The Sussexes' every move at this week's Invictus Games in the Netherlands is being captured by a film crew as part of their $200 million Netflix deal.
Ahead of their trip to Europe, the pair "instigated" talks with the other royals at Windsor Castle last week in their first joint visit to the UK since stepping down from royal life in early 2020.
Senior sources now believe the visit was a bid by the Sussexes to pave the way for "places front and centre" at the Queen's Jubilee events in June.
A Netflix crew is getting exclusive behind-the-scenes footage at the Games for a documentary – and it has sparked fears that the streaming giant could apply pressure to film the Sussexes at the Queen's celebration.
One source said, "Charles wants the Platinum Jubilee to focus only on the Queen.
"Many are disappointed that [Prince] Andrew overshadowed Prince Philip's thanksgiving service and don't want the Meghan and Harry circus to hijack the Jubilee.
"This is the Queen's show and should be about her and her 70 years of service rather than Meghan's fashion, the kids and Harry.
"They don't want it to become the Harry and Meghan show. Charles and all the family are agreed on that."
The pair have yet to confirm whether they will attend the four-day jubilee, including the annual Trooping the Colour festival.
Prince Harry and Meghan Markle put on a rare display of affection at the opening of the Invictus Games. Photo / Getty Images
It's also expected the Queen will attend a thanksgiving service at St Paul's Cathedral and will be joined by Andrew at the Epsom Derby races.
An insider added that "the royal family will be watching on at Invictus events this week concerned where Netflix will be when the Jubilee comes round".
"They will want to film behind the scenes or be in the crowd at the Jubilee as it's better footage for the documentary."
It's not yet known if Netflix or the Sussexes have issued any reassurances about the event.
Harry reportedly engineered the meeting with the royals at short notice and his reunion with Charles and Camilla lasted just 15 minutes - but his meeting with the Queen went on a little longer.
He arrived on Wednesday to stay at Frogmore Cottage ahead of the royal reunions the next morning.
But his father Charles was busy getting ready for the Maundy Thursday service where he stood in for the Queen.
The meeting with Charles was scheduled for 10am before Harry and Meghan saw the Queen for longer, sometime between 10.30am and 1pm.