To the extent so long a series over more than one person's lifetime can have a hero, the overall hero of the Masters of Rome series is Julius Caesar. He cannot properly be called a character in First Man in Rome, being seen only toward the end, as a baby. He is two years old at the beginning of The Grass Crown and thirteen by the end and us emerging as a secondary character, but a character nonetheless.
He was foreshadowed in First Man in Rome in two ways. First, when Marius has his fortune told, the fortune-teller foresees a glorious future for him, but says he will not be the greatest Roman ever; that title will belong to his wife's nephew.* Also in that novel, several leading Romans are discussing Marius with Rome's defeated enemy, Jurgutha of Numidia. Jurgutha has a high opinion of Marius but asks what if there were someone like Marius except a patrician. The others, even Marius' best friend, all dismiss the idea as absurd. We, the audience, are expected to know that there will be a patrician Marius -- Caesar. Likewise, in The Grass Crown, we meet the young Cicero, a brilliant speaker and author, but absolutely positively not cut out to be a soldier. He makes friends with young Pompey,** a fighting man but not a man of words. Young Pompey says that he supposes that Cicero's brilliance makes him too sensitive to be a soldier and just as well; he wouldn't know how to deal with anyone who was as brilliant as Cicero and a top notch soldier. Once again, we, the audience are supposed to know that Pompey will have a great friend and rival who will be as brilliant as Cicero and as soldierly as Pompey -- Caesar.
Many people have criticized McCullough for letting her admiration of Caesar spill over into outright hero worship. TV Tropes complains that he is portrayed as "smarter, tougher, stronger, braver and more morally decent than anyone else in the books by a ridiculous measure." The "more morally decent" is the one that really matters. A villain, after all, can be smart, tough, strong and even brave and still be no less a villain. These qualities just make him a more formidable villain. So how does the child Caesar rate?
Well, at the age of two, he already has an intelligence of 18 (for a two-year-old) and a charisma of 18,*** but, of course, no more knowledge or experience than any other child his age. His mother Aurelia was last seen in First Man in Rome happy and proud after having two daughters to finally have a son. We now meet her in The Grass Crown weary and run ragged, because a two-year-old with an intelligence and charisma of 18 can be quite a handful. At two years old, he already speaks complete sentences and uses big words. His mother is very strict with him because everyone else immediately falls under the spell of his charisma and indulges him. His family scrapes together the money to get him a tutor.
By the age of ten, he has taken on the very adult responsibility of helping his uncle Marius recover from a paralyzing stroke. He sometimes shows some impatience and petulance but no more, after all, than one would expect of a child shackled with such an adult responsibility. He supports his partially paralyzed and rather heavy uncle taking him walking around Rome. We are assured that he is remarkably strong for his age, but he is still just ten after all, and when they get back he collapses from exhaustion -- or does he just pretend to in order to get his aunt's sympathy? The author does not commit herself either way, but clearly his real or pretended collapse does get his aunt's sympathy, which will give him an incentive to fake it in the future.
As for his moral sense, it is hard to tell. He recognizes what a jerk his cousin Young Marius is, but he is still his cousin. He also sees Sulla for what he is -- but it is clear that that is partly because he is more than a little that way himself.
But most disturbing is the episode in which they kill the witness. According to the novel, Young Marius marched under the command of the consul, who led his troops to defeat by incompetent generalship and then refused to retreat. Young Marius then killed him and managed an orderly retreat, but was now threatened with execution on the testimony of the only witness to the incident. McCullough is clearly taking liberties with the facts here. By all historical accounts, the consul actually led his troops to an initial victory, until he was killed, at which point they fell apart, leaderless. By one account, the consul boasted that he was as good a general as the senior Marius, where upon the junior Marius killed him.
Nonetheless, in the novel Marius hears that his son is facing possible execution and decides to go investigate -- and to take a professional hitman (who is friends with the young Caesar and his mother) with him. Aunt Julia, understanding very well the implications of what this means, asks Marius not to take his nephew with him, but Young Caesar insists. They take off in a cart. Marius and the hitman wait until the young Caesar (who is still just a child, after all) is asleep before discussing the one and only witness against Young Marius. The senior Marius doesn't quite come out and say, "Someone should do something about that witness," but the message is clear enough. They arrive and ask the commander to talk to the witness. The commander has some doubts about letting the hitman go along, but Young Caesar uses his charm to persuade him. Clearly he knows what is going on. They ride by a high cliff and the hitman takes a careful action to scare the witness's horse. It rears up, and the Young Caesar grabs it by the bridle and appears to try to restrain it, but actually sends both men and horses over the edge. He grabs a tree; the others fall to their deaths. Everyone, even Marius, despite hiring the hitman to kill the witness, is convinced that it was an accident. Only Young Caesar, the hitman, and Sulla (when he hears about the incident later on) know better.
Clearly by the age of ten Caesar has a dexterity of 18 as well as intelligence and charisma. But he does not, to put it mildly, seem very morally decent! At the age of ten, he is already a party to murder. And keep in mind that neither Plutarch nor Seutonius (Caesar's earliest biographers) tell us anything whatever about his childhood. That means that this episode is fictitious, completely made up by the author. She isn't starting out by making her hero very admirable!
Also, by age 13, when Marius takes over and festoons the walls of Rome with the heads of his enemies, Young Caesar has become quite insufferable. Marius appoints him Flamen Dialis (high priest of Jupiter). As such, he was not allowed to touch iron or a horse, or to leave Rome for more than one night. All of this naturally had the effect of ruining any prospect for a political or military career. The author treats this as a deliberate attempt by Marius to prevent Caesar from having such a career, although there is no evidence that he had any such motive. Young Caesar sulks and pouts over this appointment in a very self-centered manner. He seems to care less about the savage slaughter taking place than that his future career has been ruined and now he will never be called the Fourth Founder of Rome. What a jerk! I have not done more than peek at the third book, Fortune's Favorite, but my general impression is that he becomes so insufferable in that book that you wish the conspiracy would hurry up and do its job.
How McCullough will succeed in making such an obnoxious character sympathetic remains to be seen.
*Whether this story is true is anyone's guess. The fortune teller who foretold a glorious future is mentioned in Plutarch. The part about the wife's nephew is the author's own invention.
**This appears to be historically accurate.
***The real Caesar was, in fact, extraordinarily intelligent. He was said to have known the names and faces of every soldier in his legions! He was also extremely charismatic.