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.