At the death of his father in 337? AD Constantine II became joint Emperor until 340? AD with his brothers Constantius II and Constans.
His section of the Empire was Gaul?, Britain, Spain and part of Africa. In 340? AD he marched against Constans, in an attempt to take Italy, but was defeated at Aquileia? and died.
See also Roman Emperors, Byzantine Emperors, Roman Empire and Byzantine Empire.