Siblings: Phoebe Gittins and Isaac Miller.
Shortly before being addressed by Aragorn in The Two Towers, he is standing with another Rohan adolescent. That other part was play by Henry Mortensen, Viggo Mortensen's son.
Son of Paul Gittins and Philippa Boyens - screenwriter for The Lord of the Rings.
Though he played the adolescent son of Hama in The Lord of the Rings: The Two Towers, in the book, Hama is much older, and has not only children, but a grandson as well.
His voice in The Lord of the Rings: The Two Towers (2002) was dubbed by another actor because Calum's voice had changed during filming.
He and his mother Philippa Boyens have both been involved in Best Picture winners about a King. His mother wrote The Lord of the Rings: The Return of the King (2003), while Calum appeared in The King's Speech (2010).