The royal couple broke up for a few months in 2007, with Prince William reportedly telling friends "all the fun has gone" from their relationship.
Prince William and Middleton met in college in 2001, reconciled and later got engaged in 2010, and married each other in 2011 at Westminster Abbey. After they tied the knot, the Duke and Duchess of Cambridge have had three children; Prince George, Princess Charlotte and Prince Louis.
The royal pair went to college at St. Andrews University in Scotland with Prince William studying Geography and Middleton taking History of Art. They initially were friends but things had romantic turn after discovering they share the same naughty sense of humor.
Their split in 2007 was not the first time the couple had separated: the pair reportedly split in 2004 during a summer break in college.
The duke and duchess had a "trial separation" in this period after Prince William was believed to have wanted space.
In 2007, Prince William was stationed outside of London with the Household Cavalry and experienced mounting media pressure which led them to grow apart.
The future King's behavior at clubs did not help him. He was reportedly going out many times with other guys in the barracks and was spotted on occasions drinking, dancing, flirting with women in London, which further angered Middleton. and Middleton's strained relationship and they eventually broke up in April that year.
This kept the couple from seeing each other, as Middleton grew increasingly uncomfortable with the aggressive paparazzi and press attention she was receiving as his girlfriend.
Clarence House declined to issue a statement about the relationship's end before, saying, "We don't comment on Prince William's private life."
Author Christopher Andersen in his book "William and Kate: A Royal Love Story," he revealed that Prince William broke up with Middleton over the phone while she was at work.
She excused herself from work to hear Prince William's reasons for wanting to cut ties, which were, "I can't... It just isn't going to work. It isn't fair to you."
They were both very young, Prince William explained during his engagement interview with Middleton. "We were both finding ourselves and such and being different characters and such."
Middleton reportedly fought for their relationship by "playing a waiting game one minute and then hard-to-get the next."
Post-breakup, Middleton fled the country to visit Ireland, making it apparent that she does not care.
While the duke was photographed partying with women in nightclubs, Middleton would get herself photographed looking stylish in several places.
After the split, Prince William and Middleton chose to revive their romance as they made an important pact.
The two made a secret agreement to marry each other, so Middleton had conviction after dating for years and was not yet engaged.
Related Article: Meghan Markle's Exes: What Her Past Relationships Say About Her