In February 1271, Edmund sailed with his cousin, Edmund Crouchback, to join the crusade of Lord Edward, Crouchback's elder brother. Edmund's father, Richard, already had one surviving son from his marriage to his first wife Isabel Marshal, Henry of Almain, fourteen years older than Edmund, who was originally destined to inherit Richard's lands and titles. On 13 March 1271, while attending mass at Viterbo, Henry was attacked and killed by his cousins Guy de Montfort and Simon de Montfort the Younger, sons of Simon de Montfort, in revenge for the brutal deaths of their father and older brother at Evesham. Hearing of this, the King commanded Edmund not to proceed any further and to return to England.