Compromise: Prince William Made A Touching Promise To Kate Middleton Before Their Wedding

Their marriage is just like any other, complete with agreements and understandings. While Prince William and Kate Middleton are a special kind of couple — being members of one of the world's most famous families — the Duke and Duchess of Cambridge still have to work hard at making their relationship work.

And though life changes when you join the royal family, William bucked tradition for Kate.

"Once you married into the Royal Family, you became a Windsor and that was that. Well, it was different when Kate and William got married," royal correspondent and biographer Katie Nicholl revealed in the Amazon Prime documentary Kate Middleton: Working Class to Windsor. "When William asked Kate to marry him, he made it very clear that she wouldn't have to leave her family behind her once she married into his family.

"He promised her that they'd always stay a part of the family and they have done," Nicholl added. "Whether it's joining the Queen at Ascot or being on an important barge within the Queen's fleet at the Diamond Jubilee celebrations, they've been there."

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William and Kate, both 38, tied the knot on April 29, 2011, in Westminster Abbey and later welcomed Prince George, 7, Princess Charlotte, 5, and Prince Louis, 2. The lovebirds first met as students at the University of St. Andrews in 2001.

OK! previously reported that the pair attended the same party one night where William was getting heavily hit on by another girl. Smooth as ever, Kate saw the situation and took matters into her own hands. The Duchess appeared from behind William, as she wrapped her arms around the handsome hunk and pretended to be his girlfriend. "Oh sorry, but I've got a girlfriend," William said to the other girl before he and Kate ran off together giggling.

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Kate made her intentions known once more by strutting down the runway for a charity fashion show, wearing a sheer dress that showed off her bra and underwear, for William to see. The two moved in together their sophomore year at university, and the rest is history.

In fact, the power couple remains stronger than ever as they enjoy their semi-normal lives at Kensington Palace. While they may be royalty, William and Kate try to keep their children as grounded as possible. OK! previously reported that the brunette beauty is "very chilled at home" and lives a "normal and busy" life "with kids running around and knocking things over."