Born in Cheltenham on 23 July 1872, Wilson was the second son and fifth child of physician Edward Thomas Wilson and his wife, Mary Agnes, née Whishaw. A clever, sensitive, but boisterous boy, he developed a love of the countryside, natural history and drawing from an early age. He was sent as a boarder to a preparatory school in Clifton, Bristol, but after failing to gain a scholarship to public school, he attended Cheltenham College for boys as a day pupil.