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THE VAN CUTSEM BROTHERS
The quartet of Ed, Nick, William and Hugh (along with their wives and girlfriends) are all expected to receive invites – with perhaps a special role for childhood chum Hugh. Prince William, after all, served as an usher at Hugh's 2005 wedding.
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Known as the jester among the royal court, the London nightclub owner and entrepreneur has gamely served as a chaperone for Kate Middleton when William's been away.
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Ex-girlfriend alert! William has stayed friends with this former flame (whom he dated before he went to St. Andrews), who currently works in fashion PR. Musgrave, whose father is the manager of Cirencester Park Polo Club, also went to Marlborough College with Kate.
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THOMAS VAN STRAUBENZEE
A friend of the Prince since Ludgrove prep school, "Van" continues to run in the same social circle, most recently attending the wedding of Harry Aubrey-Fletcher in January, where Will and Kate were also guests.
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An old friend and Edinburgh University grad, she went on the "Love Boat" summer cruise around the Greek Islands with William and Harry and their close friends in 1999. The interior design company owner also can lend some advice to the royal fiancé – she was recently married herself.
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Fogle – a Prince William look-alike who's been mistaken for His Royal Highness! – and his wife Marina would make a splashy addition to the big event: He's a TV presenter, adventurer and author, and she's a party planner.
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The daughter of Virgin honcho Sir Richard Branson, Holly is a friend of William's who has recently become close with Kate as well. She even offered Kate a retreat at her father's private island to escape the scrutiny following her brief split from William in 2007.
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THE TOMLINSON BROTHERS
From saddling up with William and Harry on the polo field to skiing vacations, the duo of Mark and Luke Tomlinson (whose parents own the Beaufort Polo Club in Gloucestershire) are the princes' go-to pals for all sporting adventures.
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The lone American in the group, the Nashville, Tenn., native (who now helps pal Emilia D'Erlanger run her interior design company) and her family are close to the Windsors through the horse racing world. Back in 2004, Sloan's name made headlines when William, who was already dating Kate at the time, visited her Stateside.
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A St. Andrews friend of the couple, she was once said to be dating William. When the denials came out, so did the hints that he was, in fact, with his future fiancée.