Overview
Marcus Claudius Marcellus (42–23 BC) was the eldest son of Gaius Claudius Marcellus and Octavia Minor, sister of Augustus (then known as Octavian). 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, while Marcellus caught it later, 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 imperial family whose ashes were placed in the Mausoleum of Augustus. Despite dying at a young age, Marcellus' position led to his celebration by Sextus Propertius, as well as by Virgil in the Aeneid.
Background
Marcellus was born into the Claudii Marcelli, a plebeian branch of the gens Claudia in 42 BC, the son of Gaius Claudius Marcellus and Octavia Minor. He had two full sisters named Claudia Marcella Major and Claudia Marcella Minor as well as two younger maternal half-sisters named Antonia Major and Antonia Minor.
His mother was the great-niece of Julius Caesar and the sister of Octavian. Octavian would later become the first emperor of Rome and assume the name "Augustus". His father was consul in 50 BC and, despite his initial loyalty to Pompey, sided with Caesar during Caesar's Civil War in 49 BC. After his father's death in 40 BC his mother was married to Marc Antony when Antony and her brother were the most powerful men in the Roman world.
From Wikipedia (CC BY-SA 4.0).