The Prince Of Wales is believed to 'dislike' the fact that his sons are so popular with the public, due to their ability to break tradition and connect on a more relatable level.
'Charles is unhappy the boys are openly emotive about the mental health issues they endured following the loss of their mother,' adds the insider.
Harry told Newsweek last June, 'My mother had just died, and I had to walk a long way behind her coffin, surrounded by thousands of people watching me while millions more did on television.
'I don’t think any child should be asked to do that, under any circumstances. I don’t think it would happen today.'
The source adds that Charles is regularly 'irritated' by the younger royal's informal approach.
William, Kate, Meghan and Harry are believed to call their staff by their first names - something Prince Charles reportedly does not.
Tom Bower, the author of Rebel Prince: The Power Passion And Defiance Of Prince Charles, told New Idea earlier this year, 'In public, they are all smiles, but behind the scenes they do not like Camilla and see little of each other.
'This is partly because of what happened to their mother Diana, but also because Charles spent so little time with them when they were younger.'
'William resented being told what to do and was not keen, which deepened the rift with his father,' Bower added. 'But the Queen and Prince Philip also told him that he and Harry had to increase their royal duties, and so they have done — as we are seeing now.'