His sister Marcellina

Marcellina was the elder sister of Ambrose, bishop of Milan, and one of his closest spiritual confidants. She took the veil as a consecrated virgin in a public ceremony performed by Pope Liberius in St. Peter's at Rome on Christmas Day, traditionally dated to 353, and thereafter lived a life of ascetic devotion in the city. Ambrose addressed several of his most vivid and historically valuable letters to her, narrating in real time his dramatic confrontation with the Empress Justina and the Arian court over the surrender of a Milanese basilica (385-386) and the discovery of the relics of Saints Gervasius and Protasius (386). His treatise 'De virginibus' was also dedicated to her, and she is venerated as a saint, her feast kept on 17 July.