Lucius Junius Brutus (? - 509 BC), ancestor of the Brutus who appears in this play, was the heroic founder of the Roman Republic. In 509 BC he inspired the Romans to expel king Tarquin the Proud and swear an oath to never allow another king in Rome.
The immediate cause of the rebellion against Tarquin the Proud was the rape of Lucretia, a Roman matron, by Sextus, one of Tarquin's sons. Shakespeare told Lucretia's story in his narrative poem, The Rape of Lucrece, in which Lucius Junius Brutus says of Sextus' abominations, "Rome herself in them doth stand disgraced."
Oath of Brutus by François-Joseph Navez
Lucius Junius Brutus was also known for his integrity. When courts found his sons guilty of treason and sentenced them to death, he did not object.
The Lictors Bring to Brutus the Bodies of His Sons by David