He was born in Modigliana, the third son of Frederick I Barbarossa and Beatrice I, Countess of Burgundy and brother of Henry VI, Holy Roman Emperor.
Rocca San Casciano borders the following municipalities: Dovadola, Galeata, Modigliana, Portico e San Benedetto, Predappio, Premilcuore and Tredozio.
As a Garibaldian volunteer, Lega participated in the military campaigns for Italian independence (1848–9) before resuming his training, this time under Antonio Ciseri, completing his first large-scale painting, Doubting Thomas (1850; Modigliana, Osp. Civ.).