Oates was born in Putney, Surrey, in 1880, the elder son of William Edward Oates, FRGS, and Caroline Annie, daughter of Joshua Buckton, of West Lea, Meanwood, Leeds. The Oates family were wealthy landed gentry, having had land at Dewsbury and Leeds since the 16th century; William Oates moved the family to Gestingthorpe, Essex in 1891[2] after becoming Lord of the manor of Over Hall at Gestingthorpe.[3][4] His sister Lillian, a year older,[5] married the Irish baritone and actor Frederick Ranalow.[6] An uncle was the naturalist and African explorer Frank Oates.