2. The younger son of Alexander Jannaeus and Alexandra. (J. AJ 13.16.1; Bell. Jud. 1. 5.1.) During the nine years of his mother's reign he set himself against the party of the Pharisees, whose influence she had restored; and after her death, B. C. 70, he made war against his eldest brother Hyrcanus, and obtained from him the resignation of the crown and the high-priesthood, chiefly through the aid of his father's friends, whom Alexandra had placed in the several fortresses of the country to save them from the vengeance of the Pharisees. (J. AJ 13.16, 14.1.2; Bell. Jud. 1.5, 6.1.) In B. C. 65 Judaea was invaded by Aretas, king of Arabia Petraea, with whom, at the instigation of Antipater the Idumaean, Hyrcanus had taken refuge.
By him Aristobulus was defeated in a battle and besieged in Jerusalem but Aretas was obliged to raise the siege by Scaurus and Gabinius, Pompey's lieutenants, whose intervention Aristobulus had purchased. (J. AJ 14.2, 3.2; Bell. Jud. 1.6. §§ 2, 3.)