Alypius and Nebridius
They're like the Lenny and Carl, or the Rosencrantz and Guildenstern, or the Rosencarl and Guildenlenny, of the Confessions. They essentially want the same things that Augustine wants, mostly due to his influence. Augustine is the leader of their pack so they follow him everywhere. He decides to go to Rome, and they follow; he decides to get married, and they follow suit; he decides to convert rather than get married, and so do they. Augustine is the one driving the plot, and they're along for the ride.