The indolent older son of Alexander Jannai and Salome Alexandra succeeded his father as high priest [76 BCE], while his mother retained at least nominal control of political affairs. After her death [67 BCE] he was deposed by his younger brother, Aristobulus, but with the support of Antipater he was restored to the high-priesthood after Roman forces wrested control of Jerusalem from his brother's aristocratic supporters [63 BCE]. Yet he was deprived of the title of "king" [basileus] by the Roman general, Pompey, who was opposed to monarchies in principle.
He was deposed [40 CE] by Aristobulus' son, Antigonus, who had him castrated (which under Mosaic law disqualified him from acting as priest) to preclude his restoration to the high-priesthood. Antipater's son, Herod, avenged Hyrcanus and was rewarded by engagement to the ex-high priest's granddaughter, Mariamne. Though nominally the chief Jewish official, Hyrcanus was always dominated by others: first his mother, then Antipater and finally his grandson-in-law, Herod, who ultimately had him executed on charges of treason, so that there would be no male Hasmoneans left for the new emperor Augustus to make ruler of the Jews in his stead.
Sources: Into His Own