Leonardo III Tocco was the son of Carlo II Tocco (count of Cephalonia and Zante, duke of Leukas, and ruler of Epirus) and Ramondina of Ventimiglia. On his father"s death in October 1448, Leonardo succeeded as a minor to all his titles and possessions.
He reigned as ruler of Epirus from Arta until March 24, 1449, when the city was taken by the Ottoman Turks. His mainland possessions reduced to three fortresses, Leonardo established himself in Angelokastron. In 1460, this city was also lost to the Turks, leaving only Vonitsa in the possession of Leonardo, who moved to his islands.
She was a daughter of Lazar Branković and Helena Palaiologina.
Milica died in childbirth in 1464. A new Turkish advance in 1479 captured Vonitsa and then Cephalonia, Leukas, and Zante later the same year.
Deprived of both Epirus and the Ionian Islands, Leonardo fled to the Kingdom of Naples, where he was invested with several fiefs by Ferdinand I of Naples. He died in c. 1499.
