Britain's Prince Harry and the Duchess of Cambridge have become "good pals".
The young royals often spend time together when Prince William is away working.
While the future king is said to be thrilled his wife and brother have developed a close bond, he is not always so keen on their jokes.
According to a source, Catherine and Harry have nicknamed William "Burger King" because they think he has gained a little weight.
"William loves that his wife and brother are such good pals and he jokingly calls Harry Kate's 'lady in waiting' because he is always there by her side," a source told UK magazine Grazia.
"What he doesn't enjoy, however, is how much they like to wind him up. There's always a lot of laughter when those three are together, but it's normally aimed at Wills, but he takes it well."
William and Catherine have been staying with Harry in London while their apartment is being renovated.
"Kate is a whizz in the kitchen, while Harry's skills are a little lacking. So Kate has been teaching Harry to cook rather than using the microwave," a source said.
"Aside from the silliness, they have a very brotherly, sisterly relationship."
Photos of Harry playing naked roulette in Las Vegas recently surfaced and were published world-wide.
- Cover Media
Is Mila Kunis the sexiest woman alive?Related story: (See story)