Jerome was born in Venetia and studied in Rome. He traveled to Gaul and to Israel where he became a monk in Bethlehem. He translated the whole Bible into Latin in the much celebrated Vulgate version of the Bible. It is still the only Bible recognized under the Council of Trent, even though the Roman Church allows vernacular Scriptures since Vatican II.
Ambrose became bishop of Milan in 374. He opposed Emperor Theodosius and refused to let him participate in the Lord's Supper. He is the biggest influence on Augustine, who I will mention here, but expound on later.