Flavius Valentinianus known as Valentinian II was born in 371 and was the half brother of Gratian.
Following the death of Gratian in 383, usurper Magnus Maximus who at the time was a commander of the armies in Britain, declared himself emperor of the western empire.
Valentinian fled with his mother to seek military assistance from Theodosius I who was both the ruler of the eastern empire and Valentinian’s brother in law. Magnus Maximus was killed in 388 and Valentinian’s power restored.
It was in 392 that Valentinian’s protector, Arbogast, found him hanging in his home. It was common knowledge that the two of them had argued over power over the western empire. It was this and the fact that Valentinian had previously approached Theodosius about Arbogast’s control over him that caused Theodosius to believe that this was not a suicide but murder. These suspicions were close to confirmed when Arbogast elevated Eugenius to the position of western emperor.
Eugenius’s reign did not last long as Theodosius battled him and was victorious ending in both halves of the empire being ruled by Theodosius.