The Roman Empire and its rulers profoundly shaped the history of the Western world and the political imagination of the following centuries. The names of Julius Caesar and Caesar Augustus gave rise to later titles of universal authority across Europe, from Kaiser to Tsar. Yet in their own time, they did not understand themselves as monarchs in the medieval or modern sense. Even throughout the Roman imperial period, Roman monarchy remained very different from the feudal kingship more familiar to later European history.
The rulers of the Roman Empire did not present themselves as private owners of imperial territory. They were, at least in principle, guardians and first citizens of a political and religious community. For this reason, Roman imperial power and succession followed a logic very different from later dynastic monarchy. The ability to protect public welfare, military security, and imperial order was often more important than bloodline alone. When imperial authority weakened, military commanders could openly compete for the imperial title. This made Roman dynastic succession frequent, unstable, and often retrospective: many “dynasties” were later historical summaries of connected rulers, rather than orderly hereditary houses passing power from father to son.
This chart pays particular attention to that political peculiarity. Imperator Caesar Augustus was not originally the owner of the Roman state, but the arbiter and protector of the Republic. This role emerged from the civil conflicts of the late Roman Republic. Beginning with Lucius Cornelius Sulla, military leaders increasingly intervened in Roman politics and became dominant figures within the state. After more than half a century of dictatorship, civil war, political reorganisation, assassination, and settlement, the position later called “emperor” finally emerged. Legally, however, it remained a compound of public offices, honours, commands, and rights.
For this reason, the chart begins not with Augustus alone, but with the conflicts of the late Republic. It shows the rise and fall of the First and Second Triumvirates, making visible that Augustus did not simply “found” a dynasty in the later royal sense. Instead, he gave a more stable and visible form to supreme power that had already emerged from the final crises of the Republic.
Two centuries later, this Augustan system began to break down. The Crisis of the Third Century brought nearly fifty years of instability: external wars, frequent regime changes, military rebellions, breakaway regimes, and rival claimants. These crises revealed that the empire had become too large and too militarised to be governed securely by one supreme ruler alone. An imperator was, after all, a victorious commander. In times of danger, the emperor had to be with the army, not hidden deep within a palace.
Diocletian responded by creating a more systematic form of shared imperial rule. The empire was divided between multiple emperors, who together formed a ruling college. Although the specific system designed by Diocletian collapsed even before the end of his own life, the logic of divided imperial government continued to grow stronger. Over time, it contributed to the permanent separation of eastern and western imperial courts after AD 395.
It is often assumed that in AD 395 Theodosius I simply divided the Roman Empire between his two sons, creating two separate states. This is a retrospective simplification. Before him, Constantine I and Valentinian I had also divided imperial administration between multiple rulers. Such divisions did not necessarily mean that the empire had been split into two countries. Rather, one Roman Empire was governed by more than one emperor. What changed in the fifth century was that the two parts were never permanently reunited, and the western imperial office was eventually abolished.
Even this did not mean, legally speaking, that “half of the empire” simply died while the eastern half survived as a remnant. The abolition of the western imperial office could also be understood as a return to rule by a single Roman emperor, as had happened before under Constantine I. Large parts of the western provinces were now governed by allied kings within the imperial order. Later, when Justinian I reconquered major western territories, he did not appoint a new western emperor. He ruled as emperor of the whole Roman Empire.
This chart attempts to visualise this long and complex transformation. From Diocletian onward, the eastern and western imperial lines are shown separately: the Eastern line in purple, and the Western line in red, continuing the colour of the earlier unified imperial line. This makes it possible to trace almost two centuries of division, reunion, rivalry, and political change between the two courts.
Because of space and scope, this chart covers the period from the late Roman Republic and the foundation of imperial rule to the abolition of the western imperial office, together with the contemporary eastern imperial succession up to the end of the Leonid Dynasty in AD 518. The later Eastern Roman Empire, which continued until AD 1453, will be explored in future works.
Image Credits and Copyright
All portraits, statues, coin images, and related visual materials used in this work are sourced from Wikimedia Commons. Each image is credited according to its individual licence and attribution requirements. Full image credits, licence details, source notes, and correction records are provided on the dedicated credits page.
Image Credits & Source Notes - Family Tree of the Roman Emperors
Available as a Printed Edition
A printed edition of The Family Tree of the Roman Emperors is available through the KBM Charts online shop. Designed as a large-format historical chart, the physical version allows the imperial names, dynastic lines, titles, portraits, coins, and succession markers to be read in detail.
It is suitable for close study, classroom teaching, libraries, history-themed interiors, and personal collections devoted to Roman history and classical civilisation.
