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Kate Middleton was photographed Thursday making her way to Windsor Castle ahead of Prince Harry and Meghan Markle‘s wedding rehearsal.

The princess, 36, wore a red floral-print belted shirt dress from Michael Kors and oversized sunglasses as she traveled in the passenger seat of a black car, with husband Prince William behind the wheel.

It’s the first time Kate has been seen out since giving birth to her third child, son Prince Louis, on April 23. Though she appeared on the steps of the Lindo Wing at St. Mary’s Hospital just hours after giving birth to introduce her new baby boy to the world — in heels, no less — Kate has been staying out of the public eye as the couple adjusts to live at home as a family of five.

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It’s the event of the year! Be sure to keep up with all of PEOPLE’s royal wedding coverage and don’t forget to check out everything you need to know about Meghan Markle’s perfect style.

Last Friday in a press briefing, Kensington Palace confirmed that Kate will join the wedding festivities — her first scheduled appearance since Louis’ arrival.

The palace also confirmed that Louis, who will be nearly 4 weeks old at the time of the wedding, will remain home. His older siblings, 4-year-old Prince George and 3-year-old Princess Charlotte, will have roles in the wedding as a page boy and bridesmaid.

Of course, the royal brother and sister have previous bridal party experience, having filled those roles at their Aunt Pippa Middleton’s wedding last May.

Don’t miss out! Tune in to Meghan and Harry – a Fairy-Tale Wedding on Saturday, May 19, starting at 6 a.m. ET/ 3 a.m. PT on PeopleTV — now available on PeopleTV.com and on your favorite streaming device.

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Meanwhile, even though Louis won’t be able to join in the fun, he has had a royal parade of family members visit him in the past few weeks.

Earlier this month, grandpa Prince Charles paid him a visit at Kensington Palace — his first time meeting Louis, as the 69-year-old was at his Scottish Highlands retreat of Birkhall and then had to head to France for the commemoration of the New Zealand and Australian war on Anzac Day, April 25.

The Queen, 92 — who Louis’ siblings call “Gan-Gan” — also visited her new royal great-grandson after his birth, but Prince Philip, 96, remained at home in the castle, where he is recuperating from a hip replacement operation.

Harry and Meghan will say their “I dos” on Saturday at Windsor’s St. George’s Chapel.