Aristobulus was both descendent and ancestor of Jewish kings who controlled all Palestine, but lived much of his own life outside Judea. As eldest son of Herod by his favorite wife, the Hasmonean princess Mariamne, Aristobulus was slated to be Herod's successor but fell victim to his own arrogance and court intrigues. He was barely 3 years old when his father executed his mother on false rumors of her infidelity spread by his paternal aunt Salome [29 BCE]. When he reached age 12, Herod sent him and his brother Alexander to Rome to be schooled in the household of Augustus [20 BCE].
When the handsome youths returned to Jerusalem eight years later, they attracted the adulation of many Jews. But the imperious manner of these Hasmonean princes who had lived for much of their lives at the very center of Roman imperial power frequently offended Herod and incited the jealousy of their older half-brother, Antipater III, who skillfully fed the aging king's fury with rumors of his favored sons' disloyalty. Finally in 7 BCE, after many failed attempts at reconciliation between the king and his designated heirs, the ailing Herod had Aristobulus and Alexander strangled on charges of treason and elevated Antipater to the rank of his co-regent and heir apparent. Yet Herod retained his affection for Aristobulus' children (his grand-children by Mariamne), three of whom -- Agrippa I, Herod III and Herodias — rose to prominence in the politics of the next generation of Jewish rulers.
Sources: Into His Own