According to GLOBE, the root of the bitterness is the way the Royal Family treated Beatrice and Eugenie's mother, Sarah Ferguson, Duchess of York, who was married to Charles' younger brother Andrew.
"Sarah was branded as classless," a GLOBE insider explosively tells.
The red-headed beauty was also dubbed a "money-grubber" who tried to cash in on her royal connections after divorcing Andrew in 1996.
A royal source asserts to GLOBE, "Meghan and Kate's families have been doing the same thing and getting less heat for it."
"This just fuels the heat," adds the source.
GLOBE outrageously adds Camilla has taken the opportunity to "weaken" Kate and Meghan, who she "views as rivals".
"The feud definitely threatens to tear the royal family to shreds," says a palace insider.
The Royal Family is yet to respond to GLOBE's report.