Huston was born in London, England, the son of Lady Margot Lavinia Cholmondeley and Walter Anthony Huston. His paternal grandfather was director John Huston and his maternal grandfather was Hugh Cholmondeley, 6th Marquess of Cholmondeley; his mother's ancestors include David Sassoon, the Treasurer of Baghdad, Mayer Amschel Rothschild, who founded the Rothschild family international banking dynasty, and Robert Walpole, the first Prime Minister of Great Britain. Huston is the nephew of actors Anjelica Huston and Danny Huston. He was dating English TV presenter Cat Deeley but they have now split up due to work commitments.