In 1910, he married Gladys Rosalind Cowan, OBE, the only daughter of James Cowan. Their family consisted of five children – sons James Essington and Robert Brook, and daughters Helen, Mary and Jane. His sons were educated at Geelong Grammar School and the daughters at the Clyde School. The family lived in Malvern, Victoria and owned a country property named "Landscape" near Tallarook in central Victoria. Robert Brook (1918–2009) is notable as being the Master of St Mark's College, University of Adelaide from 1957 to 1968 and the Master of Menzies College, La Trobe University from 1968 to 1970.