Has a sister called Mercy Jini Willow (b. 15 October 2001).
Nephew of actors Ralph Fiennes and Joseph Fiennes.
Has a brother called Titan Nathaniel (b. 26 August 1995).
Son of Martha Fiennes and George Tiffin.
Director David Yates says that he hired Hero Tiffin Fiennes to play the young Voldemort/Tom Riddle because of his resemblance to his uncle Ralph Fiennes (who plays Voldemort/Tom Riddle as an adult) but not specifically because he was the actor's nephew. He liked the dark haunted quality about the young actor. [USA Today - July 29, 2008].