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In 2007, after four years of dating and four years before their 2011 wedding, the royal couple hit a rough patch and decided to break it off.
Clarence House, William’s official residence at the time, declined to comment about the break up, saying it did not comment on the prince’s private life.
So what caused one of our favourite couples to split? At the time they were in a long-distance relationship, with Kate living in London and William in Dorset at army barracks.
According to the book Kate: A Biography by Marcia Moody, it was a family holiday gone wrong that led to the time apart.
Kate's family invited William to come and stay with them in Scotland for Christmas. William had initially intended to come but then changed his mind, upsetting Kate.
William spent Christmas at Sandringham with the Queen and the rest of his family - a strict royal tradition. Kate was not allowed to join in the royal family traditions unless she and William were married (although the Queen made an exception to this rule for Meghan Markle last year).
The trend of spending time apart continued into the new year, as William left to be stationed at army barracks in Dorset the day before Kate's 25th birthday in early January.
At the time many were predicting a royal wedding, the paparazzi were becoming more and more aggressive towards Kate and William was spending a lot of time partying with the rest of his barracks.
By early April, the couple had quietly broken up. It was short lived, and they were back together in June that same year after Kate attended a party at William's barracks to celebrate the end of his training.
Awkwardly, the breakup was brought up during their engagement interview a few years later.
"We both were very young, it was at university, we were sort of both finding ourselves as such and being different characters and stuff," William said in the interview.
"It was very much trying to find our own way and we were growing up, and so it was just sort of a bit of space and a bit of things like that and it worked out for the better."
Kate admitted she wasn't very happy about the split at the time, but realised in hindsight that it made her a stronger person.
"You find out things about yourself that maybe you hadn't realised, or I think you can get quite consumed by a relationship when you are younger and I really valued that time for me as well although I didn't think it at the time. Looking back on it."
As we know, the pair went on the marry in 2011 with their wedding watched live by tens of millions of people around the world and they now have three children, Prince George, Princess Charlotte and Prince Louis.
Their relationship may not have been always smooth sailing, but the break made them stronger and helped them on their way to a fairy tale ending.