The young royal sat in the box with his parents Princess Eugenie and Jack Brooksbank.
The couple made their red carpet debut at the FYC event for Lizzo's Amazon Prime Video series, 'Watch Out for the Big Grrrls.'
The couple welcomed their baby boy in September.
ET has learned that Jordan and Harvey have split.
Her Majesty's 70-year reign was celebrated with four days of events.
Mitchell and Babel also share 2-year-old daughter Atlas.
Prince George, Princess Charlotte and Prince Louis also had a front row seat for the final event of the Platinum Jubilee.
Prince Charles and Prince William each gave touching tributes, and sprinkled in some humor too.
The queen appeared in a sketch before the festivities got underway.
Cook's face was sketched more than 90 years ago before the company adopted it as its official trademark.
Lilibet turned 1 on Saturday but the Duke and Duchess of Cambridge were in Wales for other engagements.
See all the photos of the royal family at Queen Elizabeth II's Platinum Jubilee Celebration
The 31-year-old DJ has not revealed who's the father.
The visit to Wales comes on an action-packed Saturday for the queen's Platinum Jubilee.
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