Prince William and Duchess Catherine have been the poster couple for the royal family ever since they stepped out for their official engagement photo call in 2010.
But we may not have had that fairytale ending if Prince William had pursued another young lady in his university days.
In her book William and Harry, royal biographer Katie Nicholl revealed that William developed a crush on heiress and socialite Isabella Anstruther-Gough-Calthorpe when he and the then-Kate Middleton had a trial separation in their youth.
Isabella, daughter of banking heiress Lady Mary-Gaye Curzon and John Anstruther-Gough-Calthorpe, mingled in the same aristocratic social circles as Prince William and Prince Harry. In fact, her brother Jacobi was one of their polo pals and her half-sister, Cressida Bonas, famously dated Harry between 2012 and 2014 pre-Meghan.
Will and Kate famously took a break from their relationship in the early days due to the enormous amount of royal pressure and according to Nicholl, William "wanted some space" and began visiting the then 21 year-old Isabella.
"While Kate was girl-next-door pretty, Isabella boasted cover-girl looks, a title and a stately pile to boot," Nicholl writes.
"Sadly for William she had no aspirations to date a prince and despite his amorous advances declared that she was not interested ," she added.
A royal source who spoke to the Daily Mail in 2007 added that William "propositioned her several times that summer and although Isabella was single, she knocked William back and said it would be too damaging for her and her career."
Thankfully, Will and Kate had romantically reunited by the Christmas of that year and the rest, but Duchess Kate wasn't going to let everything slide.
"Word had reached her of William's visits to Isabella and she insisted that William was not to contact her again."
However, Isabella, who is now married to Sam Branson, the son of Virgin business tycoon Richard Branson, was spotted at the royal couple's 2011 wedding so it seems all is forgiven.
WATCH: Will and Kate's iconic balcony kiss. Post continues...
The Duke and Duchess even addressed their brief split in their official engagement interview.
"We were both very young, it was at university, we were both finding ourselves as such and being different characters and stuff," Prince William explained.
"It was very much trying to find our own way and we were growing up, it was a bit of space and a bit of things like that and it worked out for the better."
Kate added, "I think 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."
"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."
As for Isabella, now 38, she has worked as an actress and model and married Richard Branson's son Sam in 2013. The couple share two children together.