Royal author reveals reason Kate Middleton may not be in her sister Pippa's wedding

While Pippa Middleton is still getting used to walking around with a huge rock on her finger, she has bigger wedding problems to tend to.

In fact, there's one question on everyone's mind ...

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Will her big sis, Duchess Kate, be her matron of honor?

The 32-year-old Middleton sister, whose engagement to hedge fund manager James Matthews was revealed earlier this week, will be forced to make a big decision as to whether or not Kate will be included in her bridal party.

There's definitely chance her famous sibling, who's married to Prince William, will steal the spotlight on her special day -- and what bride would want that?

See images of the younger Middleton sister:

"Kate would upstage her sister," veteran royals author Judy Wade told People. "It's a tricky situation for Pippa. She would want her sister by her side, as who else would she trust to make things go well?"

Apparently the struggle is real when your sister is the future queen.

"She is going to upstage the bride and draw attention. Kate would want to be in the background as much as possible," Wade added.

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And rightfully so -- it's no surprise Duchess Kate is the darling of Britain and the rest of the world and people wouldn't be able to help but put all the attention on her on Pippa's big day.

Believe it or not, Pippa is also marrying into a family full of famous names.

Her future husband's brother, Spencer Matthews, is a well-known star on hit reality show "Made in Chelsea."

The Matthews family also owns the posh Eden Rock hotel in St. Barths. Something tells we'll see stunning snaps of the Middleton sisters on island in the near future -- perhaps for a bachelorette party?