The royal father and son team, who charmed crowds during George's first royal tour, received 28 per cent of the votes in a survey conducted by Debenhams, thanks to the complementary outfits they wore in New Zealand and Australia.
Designer Victoria and her two-year-old daughter Harper received 19 per cent.
Myleene Klass and her daughters Ava and Hero where named in third place, while Victoria's husband David Beckham and their three sons came in at number four.
Beyonce and Blue Ivy, Katie Holmes and Suri and Madonna and Lourdes also featured in the top ten.
The retailer said that William and George has sparked a new trend for parents and children dressing alike, with a 36 per cent leap in sales of matching outfits for mums, dads and kids.
"The mini-me trend continues to grow on the high street," said Sarah Stern, trading director for childrenswear.
"For celebrity parents and their children, being photographed is often a way of life and what better way to show that close family bond than with matching prints and designs of similarly-styled outfits."
Following in the footsteps of his mother, the Duchess of Cambridge, née Kate Middleton, the nine-month-old is already something of a fashion icon, with designers of the clothes he wore reporting a huge surge in sales thanks to the 'George effect'.