A son of Constantine I. Initially, after the death of Constantine I in 337, he shared the rule of the empire with his brothers Constantine II and Constans I. While Constantius II ruled in the east his brothers ruled in the west. Constans I usurped Constantine II and was eventually overthrown by Magnentius, a Germanic general. Constantius II eventually defeated Magnentius and became sole ruler of the Roman Empire in 353. He was also responsible for the construction of the original Hagia Sophia. He died in 361.