Morris was born at Elm House in Walthamstow, Essex, on 24 March 1834. Raised into a wealthy middle-class family, he was named after his father, a financier who worked as a partner in the Sanderson & Co. firm, bill brokers in the City of London. His mother was Emma Morris (née Shelton), who descended from a wealthy bourgeois family from Worcester. Morris was the third of his parents' surviving children; their first child, Charles, had been born in 1827 but died four days later. Charles had been followed by the birth of two girls, Emma in 1829 and Henrietta in 1833, before William's birth. These children were followed by the birth of siblings Stanley in 1837, Rendall in 1839, Arthur in 1840, Isabella in 1842, Edgar in 1844, and Alice in 1846. The Morris family were followers of the evangelical Protestant form of Christianity, and William was baptised four months after his birth at St. Mary's Church, Walthamstow.