Marcus Claudius Marcellus (42 – 23 BC) was the eldest son of Gaius Claudius Marcellus Minor and Octavia Minor, sister of Augustus (then known as Octavius). He was Augustus' nephew and closest male relative, and began to enjoy an accelerated political career as a result. He was educated with his cousin Tiberius and traveled with him to Hispania where they served under Augustus in the Cantabrian Wars. In 25 BC he returned to Rome where he married his cousin Julia, who was the emperor's daughter. Marcellus and Augustus' general Marcus Vipsanius Agrippa were the two popular choices as heir to the empire. According to Suetonius, this put Agrippa at odds with Marcellus and is the reason why Agrippa traveled away from Rome to Mytilene in 23 BC.
That year, an illness was spreading in Rome which afflicted both Augustus and Marcellus. Augustus caught it earlier in the year, and Marcellus caught it later in the year after the emperor had already recovered. The illness proved fatal and killed Marcellus at Baiae, in Campania, Italy. He would be the first member of the royal family whose ashes were placed in the Mausoleum of Augustus. Though dying young and unproven, Marcellus' position led to his celebration by Sextus Propertius and by Virgil in the Aeneid.