There's apparently one thing Kate loves mocking William about
Look, in any relationship it's important to keep your other half grounded.
For fear of someone getting notions about themselves, there's never any harm in taking a sly dig every now and again.
Even royals do it - and they don't hold back.
Kate Middleton is known to tease Prince William over the fact that he's balding.
BBC radio presenter Clara Amfo said that the Duchess was having a go at her husband over it when she met the couple last year.
"Kate had no qualms making fun of William's hair situation," Clara told Hello.
"And he took that. There was a lot of banter around that, it was very funny!"
"Prince William is the most fun royal that I've met. He's got a lot of banter actually.
"He's a very funny guy. And the banter between him and Kate, his and Kate's energy is really funny.
"They vibe off each other very well. They were like a really loving, comedy act."
It's not the first time we've heard this - it was reported last year that she likes to call him 'Baldy'.
It sounds pretty harsh but it apparently came about after he was giving out about the length of her hair compared to his.
His nickname for her, meanwhile, is supposedly Duchess Dolittle.