As Life & Style previously reported, Kate Middleton is pregnant with her and Prince William's third child. But the Duchess' younger sister, Pippa Middleton, is accusing the 34-year-old of stealing her thunder!

A source tells Life & Style that Pippa, 33, is worried the royal baby news will overshadow her upcoming nuptials to hedge fund manager James Matthews.

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"[She] desperately wants the focus to be on her rather than her sister's bump," the insider explains. "She may put off the wedding until Kate has had her baby."

For more on the royals, pick up the latest issue of Life & Style, on newsstands now! And scroll through the gallery below for a look back at Kate’s maternity style.