In 1939, Rowan was unmarried and living at
Sloane House, Chelsea. In 1944, in
Kensington, Rowan married Catherine Patricia Love, an officer in the
Women's Royal Naval Service and a daughter of Brigadier
Raymond Love, of
Mayford, and they had four children, Sarah Josephine Rowan, Susannah V. Rowan, Charles Rowan and Mark D. R. Rowan. Their daughter Susannah married Johnson Tamlyn, and their granddaughter Joanna Tamlyn married
Sir Henry de la Poer Beresford-Peirse, 7th Baronet. Their son Mark married Katharine Julia Fraser, a great-granddaughter of
Simon Fraser, 13th Lord Lovat, and they have four children. On 13 October 1964, Rowan and his wife were the last dinner guests Winston Churchill entertained at
Chartwell before his death. Lady Rowan later said of the occasion "It was sad to see such a great man become so frail". At the time of his death on 29 April 1972, Rowan was living in
Brompton, London SW3. He left an estate valued for probate at £56,422, . ==Honours==