Kate Middleton is reportedly jealous of her younger sister, Pippa Middleton. Even though the two seem to get along well in public, there’s some tension between the siblings.

In an article she wrote for The Scotsman, journalist Emma Crowning said that the Duchess of Cambridge appears to be close to her younger sister. They tend to hold hands and laugh in public, and they used to also live in the same apartment.

A source echoed Crowning’s statement by saying that Kate has always been jealous of Pippa because she’s worried that she might be eclipsed by her younger sister. Pippa is reportedly more enthusiastic, sociable and popular, especially among her brother’s friends.

And according to royal author Andrew Morton, Kate and Pippa are very competitive toward each other, just like Prince William and Prince Harry are. During her royal wedding in 2011, rumors swirled that Pippa purposely tried to steal the limelight from Kate. But Morton said that he doesn’t think this was the case.

One of Pippa’s friends from the university also told Crowning that the minute she started studying at Edinburgh, she became very particular when it comes to making friends with the right people. “She was very charming about it but quite ruthless in cultivating the ‘right’ friends,” the former student said.

“If she found out that someone had impressive social credentials — the right title, standing, connections — she would immediately pay them a lot of attention, whereas before she wouldn’t have shown the least interest,” the source added.

But despite Pippa’s popularity in school, she never escaped the criticisms of Prince William’s friends. Since some of Prince William’s peers disliked Kate, it became automatic for them to also throw shade at the future queen consort’s sister.

In an article she wrote for Vanity Fair, author and broadcaster Vicky Ward said that there was a time when Kate and Pippa were likened to the Bouvier sisters because they both wanted to “marry well.” “There are plenty of snobbish insults from people who, despite Middleton’s obvious attributes, believe that the monarchy needs to stop marrying ‘out’ of its class,” Ward said.

Kate Middleton and Pippa Middleton Kate Middleton and Pippa Middleton at the wedding of Prince William and the Duchess of Cambridge. Dan Kitwood/Getty Images