Crean was named after his uncle Dr. Thomas Joseph Crean, a successful practitioner and civil medical officer in the town of Clonmel, County Tipperary. Also from Clonmel was Lieutenant Colonel Dr. John Joseph Crean, a cousin and close friend to his father who had been with General Graham's Suakin Expedition in Sudan following the fall of Khartoum in 1885. John was a Senior Medical Officer throughout England and the colonies, also holding such positions as Principal Civil Medical Officer (PCMO) of the Straits Settlements in 1886. John was Head of the Army Medical Department in Dublin while Crean was in school at Clongowes. Crean ultimately followed in the footsteps of these two men, becoming both a successful practitioner and an esteemed officer of the Royal Army Medical Corps.