Upon the death of Augustus, Julia's paternal grandfather, Tiberius, succeeded him as Rome's second Emperor. It was during her grandfather's rule, when she was around the age of 16, that Julia married her cousin Nero Caesar (the son of Germanicus and Agrippina the Elder). The marriage appears to have been an unhappy one, and fell victim to the machinations of the notorious palace guardsman Sejanus, who exploited his intimacy with Julia's mother Livilla to scheme against Germanicus’ family. In the words of Tacitus,