Commodus had executed his sister for conspiring against him

Although Commodus was the last living son, he had four married sisters. Their spouses were always ready to become involved and hold the reins of power in the Roman Empire. The older sister, Lucilla, was the widow of the previous Roman emperor Lucius Verus. In 169 AD, Lucius perished as a result of the Antonine Plague. Even though Commodus's wife Empress Bruttia Crispina was still alive, Lucilla had held the title of Augusta (empress). There was less warfare on the empire's borders, but there was no peace within the empire. Commodus's rule was dogged by political conflict from the start, and the emperor had to foil several attempted conspiracies. She was envious of Commodus' wife, as evidenced by this. To harm her brother Commodus and his wife Bruttia, Lucilla planned a scheme.

His elder sister Lucilla desired to seize control of the Roman Empire and impose her emperorship. She solicited assistance from Quintianus and Quadratus, two men she presumably loved. She attempted to organize a coup against the emperor in 182, enlisting the help of certain powerful senators. While the emperor was at the theater, some powerful senators plotted to kill him. The task was unsuccessfully completed by the lovers, and the plot was revealed. They were detained and put to death. Lucilla, the mastermind of the plan, was banished to the island of Capri and later murdered.