Royal watchers know Prince Charles initially didn't have a good relationship with Prince William and Prince Harry. However, who would have thought that the royal princes would disrespect their father so much?

Prince Charles, being the heir to the throne, had a detached relationship with his two sons because his royal duties took much of his time.

Royal biographer Penny Junor previously told the Daily Beast that the Prince of Wales focused on his work too much that he has overlook his loved ones and friends. So when Princess Diana suddenly succumbed after a tragic car accident in 1997, he underwent a massive change so he could do the parenting of his two sons alone.

However, the death of the Princess of Wales only triggered the two William and Harry to challenge their father's authority even more.

According to Daily Mail columnist Richard Kay, Prince William and Prince Harry would always show an aloof approach to their father and upstage him most of the time.

"For Charles, who at the age of 48 and set in his ways found himself a single parent to two teenage boys, the years after Diana's death were tricky," Kay told the Daily Mail earlier this 2020.

Prince Charles reportedly struggled so much to be a strict parent, and his sons ridiculed him even more with their behavior.

Rather than respecting him as a father and as an heir to the throne, Prince William and Prince Harry did't care and even referred to him as a fogey.

"With so much of his own life regimented and given over to royal duty, who could blame him if he took an easy route with his sons? His attitude was to take the path of least resistance. This sometimes allowed him to be seen to be weak, and as the boys got older they would exploit it," the royal correspondent went on.

William and Harry continued to show Prince Charles little respect through the years, so much so that they even broke the royal family's golden rule of not stealing the spotlight from a member of the royal family.

The royal siblings upstaged the Prince of Wales multiple times. For instance, when Prince Charles was doing an important business on behalf of the U.K. government, the two got everyone's attention by making their own headlines.

"Of course, he didn't say anything. He was angry and hurt, but he was never as decisive as he should have been," Kay revealed.

Prince Charles "Hurting" Until Now

Even now that the two have grown older, Prince William and Prince Harry still managed to torture their father's emotions.

According to Page Six, when Prince Harry announced his departure as a senior royal member, Prince Charles was firmly at odds with the decision that left him "floored." His son's sudden relocation also reportedly affected him so much.

Meanwhile, Prince Charles also felt resentful toward Prince William since he and his family spend more time with the Middletons. He also complained that "he does not see George anymore."

"When William and the family nipped off to Courchevel for a few days' skiing at the star of the year, Charles had no idea they were away. He was rather hurt," Katie Nicholl told Daily Mail in 2016. "Neither of them pick up the phone to each other and weeks can pass without them having a proper catch-up."

READ MORE: King's Doom: Prince Charles DEVASTATED After Prince Harry Heartbreak