Three men named Marcellus
The first important Marcus Claudius Marcellus was a Roman general at the end of the third century BCE. He actually became prominent before the Hannibalic war, when he killed the king of a Celtic tribe in single combat during a cavalry battle: because Marcellus was in command of his army, he was allowed to dedicate the king's armor in the temple of Jupiter Feretrius as spolia opima, only the third Roman since Romulus to do so. (And it becomes even more impressive when you consider the issues with the historicity of Romulus!)
That feat is typical of Marcellus: daring, aggressive, successful. His is one of the voices arguing against Fabius Maximus' policy of avoiding contact with Hannibal -- and in fact Marcellus is responsible for raiding Hannibal's forces after Cannae -- and they were political rivals as well, with Marcellus as one of the first models of the "popular" politician and Fabius as his aristocratic opponent. Not that Marcellus was incapable of patience (see: the siege of Syracuse) or lacked interest in matters beyond war and politics (see: his reaction to the murder of Archimedes and his decision to display the artistic booty from Syracuse where all Romans could see it), but mostly, he was what he was: general, politician, triumphator, consul 5 times. He was killed in a cavalry skirmish with some of Hannibal's troops.
Plutarch's biography of Marcellus is available here on Lacus Curtius; there is also a nice chapter on Marcellus' politics in Myles McDonnell's Roman Manliness: Virtus and the Roman Republic (Cambridge 2006).
Marcus Claudius Marcellus, son of Marcus, was the consul of 51 BCE and one of Caesar's fiercest political opponents and main rivals in oratory. He was part of an extremely successful family, at least in the short term: his cousin Gaius Claudius Marcellus (son of Gaius) was consul in 50, and his brother, also Gaius Claudius Marcellus (son of Marcus) was consul in 49. (I think that the Gaiuses go in that order, but am not 100% sure -- someone with Broughton's MRR can tell me!) The three of them must shoulder at least some of the blame for preventing any reconciliation between Pompey and Caesar during these years.
Marcus went into exile after Pompey's defeat at Pharsalus, and it was only with great difficulty that Cicero persuaded him to ask Caesar to be allowed to return to Rome -- largely by suggesting that Rome under Caesar's dictatorship was as much a place of exile as Mytilene. In the end, Marcellus agreed, and Gaius (his brother) engineered a scene in the Senate which forced Caesar to recall his former opponent. Cicero gave a speech praising Caesar's decision, the Pro Marcello -- the speech is frequently misinterpreted as either abject flattery or a veiled attack, but I would say that it's better read as one part of a complicated political negotiation about the future of the Roman res publica.
Marcellus was murdered in Athens on his way back to Rome, apparently in an argument about money with a client of his. Like his ancestor above, he was in his own way an exemplar of proper Roman aristocratic behavior: hard-headed, uncompromising and proud. We find Brutus' comment on him preserved in Cicero: "I saw the man recently on Mytilene, and as I have said, I really saw a man." (Cicero, Brutus 250)
Cicero's letters to and about Marcellus are scattered through the Letters to His Friends -- the ones focusing on his return are IV.7-11 (Shackelton Bailey nos. 229-233); the speech on Marcellus' return is available on Perseus, here.
Despite the family's political opposition to him, Marcus' brother Gaius was married to Octavia, Caesar's great-niece and the sister of the future emperor Augustus; they has a son, Marcellus. (I find him online as Marcus Claudius Marcellus, son of Gaius, but Syme has the more plausible Gaius Claudius Marcellus for him. And I think that the father is Marcus' brother, not his cousin) As Augustus' nearest male relative, he was offered early promotion and favor, and married to Julia, Augustus' only child. He was in some loose sense Augustus' heir, although what that entailed outside the (extensive!) family property was, in the 20s BCE, rather nebulous; to make up for this problem, Augustus planned that he would have early access to important offices -- the consulship at 23, a full ten years earlier than the norm for the period. But when deathly ill in 23 BCE, Augustus left his seal-ring to (and instructions for) Agrippa, rather than to Marcellus: perfectly reasonable, since Agrippa would have had a much better chance of maintaining order had Augustus died. In any case, Marcellus died in the same year, aged 19; Octavia and Augustus were both devastated.
He appears in Book 6 of Vergil's Aeneid, as part of a parade of Roman heroes who appear to Aeneas in the Underworld -- the last of them, in fact, in the company of his ancestorrcus Claudius Marcellus. When Aeneas asks, Anchises tells of his great potential and early death:
"...No youth
born of the seed of Ilium will so
excite his Latin ancestors to hope;
the land of Romulus will never boast
with so much pride of any of its sons.
I weep for righteousness, for ancient trust,
for his unconquerable hand...
O boy whom we lament, if only you
could break the bond of fate and be Marcellus."
(trans. Mandelbaum)
Marcellus' presence there is a puzzle -- he hardly seems to belong in the catalogue of kings and generals! The simple answer is that Vergil inserted Marcellus simply to please Augustus, his patron, but that is to underestimate both Vergil's talent and his patron's sense -- the passage serves a far more important purpose within the poem than that. The whole journey to the underworld is a strange episode, full of past sorrows and false starts, and the vision of future heroes is no exception; the confusion between past, present and future is typical of the Aeneid, and particularly of the second half of the poem. Vergil's decision to end on a note of sorrow, not of triumph, is also typical of the Aeneid -- the whole Roman project, as suggested in the opening of the poem, is a matter of labor and uncertainly, and no matter how often Roman triumph is predicted, it is as often undercut. Unbounded empire? Perhaps, but not without Marcellus, and Rome will be without Marcellus.
The same uncertainly is introduced at the end of the book, of course, when Aeneas and the Sybil emerge through the gate of false dreams, not true spirits -- because they are alive, or because the whole prophecy is worthless? Vergil doesn't say. And that leads Aeneas back to Italy, to civil war, to victory and defeat.
This post brought to you by the work I should be doing, and the fact that I have been reading things I should not have been reading.