Their relationship in the early days suffered rocky moments and was on a downward spiral before the break-up.
The pair who were only in their early twenties at the beginning of their courtship, still had a thing or two to learn about love.
After both attending St Andrews University in Scotland, William went to serve in the military for a while and it meant being stationed a fair distance apart from Kate.
They naturally felt a distance between them, and there have been previous unfounded reports that William had a wandering eye.
After a period of being apart, Kate felt as though they never got to really spend much time together and in early April they broke up.
However, the couple realised they couldn't live without each other and reunited just four months later.
A close friend told the Sun at the time: "He is only 24 and simply wasn't ready to settle down.
"He has always had a roving eye...that's something Kate had always known and accepted - it was part of the deal, if you like."
The nightclub outburst from William alerting a media frenzy that ensued for four months before the pair reunited.
According to royal author Katie Nicholl, Kate was "hurt deeply" when Prince William secretly paid a visit to "exquisite-looking" socialite Isabella Calthorpe during their separation.
However, the British socialite spurned his advances, as she had no "aspirations to date a prince despite his amorous advances."
William has said of their split previously: "We were both very young.
"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."
Kate has also provided insight into the relationship, as she said it was a tough time.
"At the time, I wasn't very happy about it but actually it made me 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."
After rekindling their relationship they have appeared the picture of domestic bliss, until last year when the duke came under scrutiny for a supposed affair with family friend Rose Hanbury.
Which he has vehemently denied and the rumours were never proven.
As of late, they have proved their relationship is stronger than ever as they have been at the forefront of royal duty.
They have recently had to deal with Prince Harry's departure with wife Meghan Markle to the US and Prince Charles being diagnosed with coronavirus.
However, they have continued to help citizens of the UK, as they worked together with Mind Charity that helps those with mental health.
Prince William and Kate Middleton are known for their rock-solid and happy relationship that has lasted for nearly 20 years.
However, it has been claimed that the future monarch didn't always feel that way.
Back in 2007 when the pair split for the first and last time, Prince William was reportedly elated to be "free" from his relationship with Kate.
William immediately went back to his old partying ways with his friends after the breakup.
He joined friends at Mahiki nightclub in London and according to online news site Parade, was spotted jumping on a table shouting: "I'm free!"