The 31-year-old Duchess of Cambridge wore a gown by British designer Sarah Burton for Alexander McQueen's fashion house.
''Kim is absolutely obsessed with everything Kate and William do. She considers her own family 'American Royalty'. Kim loves Kate's style and while she is planning on several gowns for her big day, she wants the one for the ceremony to look something like Kate's dress. The brief is demure princess and she'll also wear a tiara," a source told Grazia magazine.
The 33-year-old Keeping Up with the Kardashians star and fiance Kanye West, are also are planning to sit on "golden thrones" during their reception.
"They think it'd be really cool to have gold thrones to sit on during the reception. They've already got a Buckingham Palace-themed room in their new home, which they're using as inspiration," the insider added.
The 36-year-old singer, who welcomed daughter North with the Kardashian, had also compared her to royal baby Prince George.
"My daughter is in a position of a level of royalty like the Prince and Princess in London," he earlier said during a chat with Power 105's The Breakfast Club.
Previously it was reported that West, famous for his jewellery and ostentatious lifestyle, views the Duchess of Cambridge as a fashion icon, and wants Kardashian to follow her elegant English style.
"Kanye has been urging Kim to tone down her make-up and style her hair in a more conservative style, like Kate," a source told The Daily Star. "And it's not just Kate's regal look that Kanye wants Kim to mimic. He's also told her that she could learn a thing or two about poise and sophistication from Kate.