Renowned actor Ralph Fiennes (Harry Potter's Lord Voldemort) and Britain's Prince Charles 17 Pairs of Celebrities You Probably Didn't Know Were Related. His sister, the film-maker Sophie Fiennes, says her son Horace, now eight, really enjoyed the sword fighting in his Richard III, which is, if you think. Talented actor. Younger brother of Ralph Fiennes. Starred in movies such as "The Merchant of Venice" and "Shakespeare in Love." Played Agent Mark Benford. His siblings include actor Joseph Fiennes, director Martha Fiennes, composer Magnus Fiennes, composer Sophie Fiennes, and conservationist Jacob Fiennes.