There were definitely twin emperors! But it seems as though one ... saw five different claimants vying for control of the Roman Empire. Commodus, who actually did fight as a gladiator for shiggles ...

Lucius chafes against Rome's carnivorous nature represented in Acacius, the depravity modeled by its twin emperors, and its social order embodied in Macrinus, a former slave who has clawed his way ...

When the Roman Empire began collapsing, Christianity prevailed and the Roman Catholic Church kept its territories together.

The results were remarkably successful. Nerva became emperor immediately after Domitian’s murder in 96 AD. He had a lifetime of service to Rome and its emperors, and had served as consul twice ...

The first answer is simple: hereditary rule. For most of this period, emperors were not chosen on the basis of their ability or honesty, but simply because they were born in the right family.