And what a journey their romance has been! Six years ago, a Prince married his Princess and it was the stuff of dreams.
After meeting a young Kate Middleton at St Andrew's University back in 2001, the pair became fast friends before becoming a couple two years later.
In 2010, a besotted William popped the question on a trip to Kenya. Since Prince William and Duchess Catherine's lavish wedding ceremony, they've travelled all over the globe while working tirelessly on issues like mental health, child bereavement and equality.
But their biggest adventure was when they welcomed their two children - Prince George and Princess Charlotte.
Now they're toasting their teacups once again as they count down to their third child, who is reportedly due in March, 2018.
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To celebrate the new royal baby, relive Prince William and Duchess Catherine's cutest moments in pics! Keep scrolling...