Britain's Duchess Catherine is obsessed with 'Keeping Up With the Kardashians'.

The 31-year-old royal - who was known as Kate Middleton before her marriage to Prince William - has begun tuning into the show after she learned Kim Kardashian, who, like the duchess, is expecting her first child in July, is a big fan of hers.

A source said: ''Ever since Kim started mentioning Kate a lot in public, she has started watching 'Keeping Up With the Kardashians' religiously.

''She thinks the family are hilarious. People forget Kate is just a normal girl who married into royalty and enjoys the same trashy TV shows most people do.''

However, Catherine hasn't been able to get her husband to watch the show with her and he has been ''making fun'' of her new obsession.

The source added to the Daily Star newspaper: ''Will doesn't watch the show with her and makes fun of her for liking it so much.

''It doesn't bother Catherine though. She finds it relaxing and is flattered Kim keeps speaking so highly of her.''

It was recently claimed Kim - who is in a relationship with Kanye West - had sent the duchess a maternity gift because she was so excited to learn they are both expecting their babies in July.

A source said: ''When Kim found out the pair had similar due dates, she got incredibly excited.

''She had her PA write a kind, warm note to Kate, enclosing a gift for the future heir to the throne and explaining they were both due in July.''