Kate Middleton wasn't happy with Prince William partying habits, and it apparently even caused their split in 2007, according to a biographer.

Jessica Jayne claimed in her book, "The Duchess of Cambridge: How Kate Middleton Became A Future Queen," that Middleton was "humiliated" by Prince William's partying. Three years before their engagement, Middleton quit her job at fashion house Jigsaw because she needed "some time to think about her relationship with William."

The Duchess of Cambridge reportedly started to doubt the royal prince when she learned that he was going clubbing with his friends instead of seeing her. They decided to finally split after Prince William was photographed getting too close with two girls in a nightclub.

"Kate was further humiliated when a photo of William with two girls was published in tabloids," Jayne said (as quoted by Express).

Prior to their 2007 breakup, Jayne said that the Duke and Duchess of Cambridge had a trial separation back in 2004.

According to Jayne, Middleton was miserable after learning that Prince William decided to join an all-boys holiday trip with his friend Guy Pelly. The duchess reportedly "never thought highly of" Pelly and even considered him a bad influence on the royal.

The royal mom of three was so devastated that she packed her bags and returned home to Berkshire to spend the summer with her family. She also let her guard down with her friends. One of them revealed that Middleton got drunk and was debating whether she should text or call Prince William.

However,  Sun's former royal editor Duncan Larcombe has another opinion about Prince William and Middleton's split at that time. According to him, Middleton's family background might have played a part in their separation.

"They used to say 'doors to manual' whenever they saw Kate Middleton," Larcombe said, reportedly referring to Middleton's mother, Carole, who was a former airline hostess. The palace vigorously denied this, but Larcombe insisted that "one or two people in William's inner circle may have that view."

When Prince William and Middleton announced their engagement they addressed the split. According to Prince William, they parted ways because they were still figuring out what they want in their lives. He also added that their age at that time was another factor.

"We were both very young," Prince William said. "It was at university, we were sort of both finding ourselves as such and being different characters and stuff, it was very much trying to find our own way and we were growing up."