The sister of Kate Middleton, Pippa Middleton and her husband James Matthews, and brother James Middleton, are seated next to the main entrance.
The first cheers of the morning erupted in Horseshoe Cloister at the arrival of the groom’s parents to St George’s Chapel.
Blustery conditions saw Jack Brooksbank’s mother momentarily hold onto her hat as she climbed the steps.
The Duchess of Cambridge arrived with the duke wearing a dress by Alexander McQueen and a Philip Treacy hat, while the Duchess of Sussex, who arrived with Harry, was dressed in a navy dress and coat by Givenchy and a hat by Noel Stewart.
Members of the royal family arrived in a group with Zara and Mike Tindall among the group along with Peter and Autumn Phillips.
The evening reception is likely to be “one hell of a party”, the wife of the Duke of York’s head gardener said.
The festivities are expected to continue into the early hours with an evening party at the York family home, the Royal Lodge in Windsor Great Park.
Tracey Lisk, who is married to Andrew’s head gardener Mark Lisk and lives in the park’s grounds, said: “The setup looks amazing so I’m sure it will be one hell of a party.”
While Mr Lisk took a seat inside St George’s Chapel, Mrs Lisk joined her stepdaughter Mica just outside in Horseshoe Cloister alongside other members of the public including representatives from charities close to bride and groom’s hearts.