As far as we know, Marcus Aurelius grew up in a period of general peace and tranquility. But so did his adoptive brother, Lucius Verus. When the emperor Antoninus Pius died, both men--Marcus and Lucius--had claims to the empire. But could Rome really function with two emperors? The Roman Senate thought Marcus alone should rule. Adding to the awkwardness of the transition, the Parthian empire attacked Rome's client state Armenia. An all out war would follow; but first the Romans needed to resolve their leadership situation.