Prince Charles and Prince Harry
Prince Charles admitted that he struggled with the idea of being a father of two after Prince Harry's birth. Pictured: Prince Charles and Prince Harry laugh during the Invictus Games Opening Ceremony on Sept. 10, 2014 in London. Getty Images/Chris Jackson

Prince Charles struggled with fatherhood after Prince Harry's birth.

The Prince of Wales wrote a letter to a friend named "David" on Oct. 16, 1984, just a little over a month after Princess Diana delivered Prince Harry. In the letter, Prince Charles talked about the overwhelming support they received from the public and spoke about the new adjustments in the household after welcoming a new baby into the family.

"Dear David, warmest thanks to you & Irene for thinking of sending such a nice congratulatory letter following Harry's birth," Prince Charles wrote (via Daily Star). "We have been overwhelmed by everyone's kindness & enthusiasm & my poor office has vanished under a deluge of cards, letters & endless pairs of booties."

However, he also confessed that he has yet to get use to the idea of having two children. "We are thrilled with our new arrival, but can't get used to the idea of being a father of two - it all seems much too grown up somehow!" he added. "I do hope all goes well with Jon & please give my love to Irene. Love, forever Charles."

According to Andrew Morton's biography "Diana: Her True Story," Prince Harry's birth was a factor in Prince Charles and Princess Diana's troubled marriage. The People's Princess was reportedly hurt when the Prince of Wales exclaimed, "Oh God, it's a boy," because he wanted to have a girl for their second child.

Prince Charles even complained to Princess Diana's mom, telling her that he was "so disappointed - we thought it would be a girl." The future king explained that it was just a joke, but Princess Diana was still hurt by his behavior. After the incident, she admitted that "something inside me closed off," and their marriage broke down shortly after that.

Princess Diana knew all along that she was expecting another boy because she saw the scan. But she kept it a secret from Prince Charles because he was very open about his preference of having a girl.

In related news, Princess Diana was very creative and naughty when it comes to giving her sons presents. The princess was reportedly fond of hilarious and outrageous gifts. "She'd spend hours looking for jokey things for their stockings. One year, Harry got fake dog poo," Paul Burrell said.

One time, she also gave Prince William a boobs cake on his 13th birthday. The Duke of Cambridge was caught off guard and turned red.

"The Princess loved embarrassing people in the nicest way, in a fun way, whether it was telling a dirty, risqué joke – which usually got me. William just went bright-red," Darren McGrady said.