 He was the son of William Bradley Isham (1827–1909) and Julia (née Burhans) Isham (1827–1907).His father was a leather merchant who owned downtown factories and warehouses on Gold and Cliff Streets, and became vice-president of the Bank of the Metropolis and the president of the Bond and Mortgage Guarantee Company.Among his siblings was Charles Bradford Isham, who married Mamie Lincoln (granddaughter of Abraham Lincoln); and Julia Isham, who married historian Henry Osborn Taylor.