 Gran was married three times.Firstly, on 29 April 1918, in London, to actress Lily St. John (Lilian Clara Johnson), marriage dissolved 1921; secondly in 1923 to Ingeborg Meinich (1902–1997) with whom he had two daughters, the marriage dissolved; lastly in 1941 to Margaret Schønheyder, a renowned portrait painter.With his last wife, he had a son, Hermann who was born in 1944.