Prince Charles and Prince Andrew may be siblings, but the two couldn’t be more different from each other.

Royal author Andrew Morton touched on the differences between the royal siblings in his 1993 book “Andrew: The Playboy Prince,” saying that Prince Andrew was a “mummy’s boy.” The term is something that can never be used in reference to Prince Charles.

“Andrew is very likable but he is very conscious of being a royal. He’s a bit of a mummy’s boy – you could never say that about Charles… Charles would never need encouragement to join in the fun and he certainly wouldn’t talk about girl conquests,” he said.

Queen Elizabeth II and Prince Philip decided to send both Prince Charles and Prince Andrew to Dartmouth Naval College. While there, the siblings received unfavorable comparisons. Prince Charles, who was a favorite at the institution, set the bar high for his younger brother.

According to Morton, when Prince Andrew first arrived at Dartmouth, he was resented by some fellow recruits. The dad of two was disliked because he played the “I am a Prince” routine and seemed rather arrogant.

A wife of a Dartmouth instructor also told Morton that until today, Prince Charles is remembered at the school with tremendous affection. Prince Andrew, on the other hand, isn’t as popular with both the staff and his fellow cadets.

“His brother was a great practical joker but his brother walks away from anything like that. He never lets you forget who he is,” the source said.

Meanwhile, Morton also revealed that the comparisons between Prince Charles and Prince Andrew were a strain for the latter, especially during his younger days. Since Prince Charles did a lot of things first and was great at it, Prince Andrew usually just came second and didn’t do things as well as the heir to the throne.

At one point, he earned the unflattering nickname “Action Man Two,” which was something that he wasn’t particularly fond of.

Prince Andrew, Prince Charles
Pictured: Princes Andrew, Charles attend the Order of the Garter Service at St George's Chapel in Windsor Castle on June 15, 2015 in Windsor, England. Getty Images/Peter Nicholls-WPA Pool