Arcadius was born in 377 in Hispania, the eldest son of Theodosius I and Aelia Flaccilla, and brother of Honorius. On 16 January 383, his father declared the five-year-old Arcadius an Augustus and co-ruler for the eastern half of the Empire. Ten years later a corresponding declaration made Honorius Augustus of the western half. Arcadius passed his early years under the tutelage of the rhetorician Themistius and Arsenius Zonaras, a monk. Arcadius is not well liked by his brother Honorius.