Sykes' twin sister Lucy, who moved to New York in 1996, became fashion director of "Marie Claire", and later a designer of children's clothes. In the late 1990s the Sykes sisters were sometimes described as the "twin set". Sykes later joked, with reference to the heiresses Paris and Nicky Hilton, that "Lucy and I were Paris and Nicky without the sextape" (an allusion to the sex tape featuring Paris Hilton and a former boyfriend that had been posted on the internet in 2003). Lucy Sykes married Euan Rellie, a New York-based investment banker, in 2002.