And, according to reports, the Duchess was recently so concerned for her bro-in-law, she stepped in and dished out some handy relationship advice.
After the prince's relationship with Cressida Bonas came under scrutiny with rumours it was on the rocks, Kate reportedly stepped in and told the hairy royal to put on a show of togetherness.
According to the Irish Independent, a source told Look magazine: "Kate knows all too well how damaging false reports can be. So she urged them to show the world they were still going strong before the story snowballed."
Kate has successfully navigated the media since being catapulted into the public eye with her high-profile romance with Prince William, so we suggest you take her advice, Harry.
Meanwhile, perhaps he better not follow in her footsteps regarding Valentine's Day plans if he wants to keep Cressie happy.
Rather than spending the day with her hubby, Kate will reportedly be opening The ICAP Art Room at Northolt High School in West London. Not so romantic.
However, the couple will have some quality time together when they jet off in April for an official tour of Australia and New Zealand.
In the meantime, Kate's soaking up the Caribbean sun in Mustique with little Prince George on his first exotic holiday with mum and the Middletons.
Love Kate? Flick through her top 2013 pictures right here: