Tiarks married Emmy Maria Franziska Brödermann of Hamburg, Germany, on November 18, 1899.
Among his appointments were a directorship of the Bank of England (1912-1945); a partnership in J. Henry Schröder and Co; a partnership in the Anglo-Iranian Oil Company (1917-1948); and High Sheriff of Kent (1927.
Tiarks was reputedly a member of the British Union of Fascists and an associate of Oswald Mosley. He was also a member of the Anglo-German Fellowship.