The son of Lucius, Young Lucius is Titus's grandson and Lavinia's nephew. He appears in only a few scenes in the play, but these appearances occur at crucial moments in the plot.
It's during Young Lucius's story time in Act 4, Scene 1 that Lavinia finds a way to reveal that she was raped by Chiron and Demetrius. (She gets her stumps on a book containing Ovid's story about the rape of Philomel in Book 6 of Metamorphoses.)
After Lavinia identifies Demetrius and Chiron as her attackers, Young Lucius makes a disturbing declaration:
I say, my lord, that if I were a man,
Their mother's bed-chamber should not be safe
For these bad bondmen to the yoke of Rome. (4.1.5)
Yikes! When Young Lucius declares the means by which he would avenge his aunt's rape (by storming into Tamora's "bed-chamber" for payback), we can't help but be disturbed. Lucius is only a child, and yet his family's involvement in a blood feud is teaching him to carry on the cycle of revenge-fuelled violence.
Young Lucius in Titus (1999)
Is this the point that director Julie Taymor is making at the end of Titus, a modern adaptation of the play? In the film's final moments (which don't occur in the play), Young Lucius removes Aaron's baby from a cage and walks out of the Coliseum. Is Lucius going to behave like his elders and do something horrible to the baby, or is he going to be the one to finally break the cycle of violence?