He was son of Henry Frederick Tiarks (23 December 1832 - 18 October 1911), banker, partner in J. Henry Schröder & Co. in London, and wife Agnes Morris (1840 - 5 February 1923), adopted daughter of Alexander Schlüsser, partner in J. Henry Schröder & Co. in London, paternal grandson of Johann Gerhard Tiarks, chaplain of the Duchess of Kent.
Resigned his commission following the death of his elder brother, to join his father in business.
[2] He served in World War I under Sir William Reginald Hall, Director of Naval Intelligence, in Room 40 Admiralty, as Lieut.-Cmdr.
[3] Of German descent himself, like his wife, he was also listed as a member of the Anglo-German Fellowship, of the British Union of Fascists but also in Hitler's 'Black Book'.
[4] Tiarks married in Hamburg, Germany, on 18 November 1899 Emmie "Emmy" Marie Franziska Brödermann (15 February 1875 – 27 July 1943), daughter of Eduard Matthias Brödermann, merchant, and wife Ramona Luisa Clara Ignacia Störzel.