 Hewlett married Hilda Beatrice Herbert on 3 January 1888 in St Peter's Church, Vauxhall, where her father was the incumbent vicar.The couple had two children, a daughter, Pia, and a son, Francis, but separated in 1914, partly due to Hilda's increasing interest in aviation.In 1911, Hilda had become the first woman in the UK to gain a pilot's licence.