Prince Charles and Prince Philip were never close. In fact, the Duke of Edinburgh hated one thing about his eldest son.

In the book “The Firm,” royal expert Penny Junor said that the fact that the heir to the throne is fundamentally a weak man incensed Prince Philip. After Queen Elizabeth II gave birth to a boy, Prince Philip wanted him to be a reflection of who he was.

“A tough, abrasive, plain-talking, unemotional man’s man — but those qualities bypassed his first son and settled instead on his daughter,” Junor said. “Charles has a generous heart, he cares hugely about the underdog, because, for all his partial living, he is one, he identifies,” he added.

Prince Charles has always wanted to make the world a better place to live in. He also wants the public to stop feeling helpless and hopeless. He is very passionate about the environment, as well as climate change.

“He is admirable in so many ways, but he has never been able to cope with confrontation. Blisteringly angry at times, certainly, demanding, yes, and on the sporting field no one could question his courage, but he has never been brave when it comes to taking tough decisions. He gets others to do it for him,” he said.

Prince Charles Prince Charles, Prince of Wales, speaks during the Governor-General’s Reception at Government House. Prince Charles might not be the next king, according to former royal butler Paul Burrell. Chris Jackson/Getty Images

Prince Philip, on the other hand, was his eldest son’s opposite. He had a wicked sense of humor, and he also spoke his mind at all times. The Duke of Edinburgh has also been branded as rude on multiple occasions. During an interview, the Queen’s husband even acknowledged the fact that he is rude.

At the age of 21, he wrote a letter to a relative whose son had been killed in the war. “I know you will never think much of me,” he said. “I am rude and unmannerly and I say many things out of turn which I realize afterward must have hurt someone. Then I am filled with remorse and I try to put matters right,” he added.

Meanwhile, there’s one child of Prince Philip that he’s reported to be close to — his only daughter, Princess Anne. The two royals are said to have similar personalities.

Prince Philip Britain's Prince Philip, Duke of Edinburgh, in his role as Captain General, Royal Marines, attends a Parade to mark the finale of the 1664 Global Challenge on the Buckingham Palace Forecourt in central London on August 2, 2017. YUI MOK/AFP/Getty Images