Wikipedia
According to Livy, the Horatii were male triplets from Rome. During a war between Rome and Alba Longa during the reign of Tullus Hostilius (approx. 672-642 B.C.), it was agreed that settlement of the war would depend on the outcome of a battle between the Horatii and the Curiatii. The Curiatii were male triplets from Alba Longa and of the same age as the Horatii.
In the battle, the three Curiatii were wounded, but two of the Horatii were killed. The last of the Horatii, Publius, turned as if to flee. The Curiatii chased him but, as a result of their wounds, became separated. This enabled Publius to slay them one by one.
When the victorious Horatius returned carrying the spoils of victory, his sister cried out in grief because she realized the Curiatius to whom she had been engaged was dead. Then Horatius killed his sister, proclaiming, "So perish any Roman woman who mourns the enemy." For the murder, he was condemned to death but, upon the advice of a certain jurist named Tullus, Horatius appealed to the assembly of the people. Horatius' father, also called Publius, spoke to the people of his son's recent victory, and entreated them not to render him childless since he now had only one of four children. Persuaded by his father's arguments, the people acquitted Horatius. The legend might have been the reason for the condemned in Rome to be able to appeal to the populace. His father was required to expiate the crime by offering sacrifices, which were thereafter continued by the gens Horatia, and the son was required to pass under a beam laid across the street, as if a yoke, which remained in the city and became known as Sororium Tigillum, the "sister's gibbet".
The spoils of the Curiatii were hung in a place that became known as Pila Horatia.