He was the son of Graham (the postmaster). Gillies was married on 17/11/1892 in Bunbury to Elizabeth Wisbey (12/05/1870-). Elizabeth was born in York West, as the daughter of Charles and Ellen. Well known as a prospector who led a party financed by Dr J. W. Hope to inspect Kimberley goldfields between 1886-1887. Prospected again in 1890 at Southern Cross and discovered Hope's Hill. Disputed Connolly's claim to a reward for the discovery of Hutchison goldfield.