Mariamne's brother Aristobulus, a favorite of the people on account of his noble Hasmonean descent and handsome presence, had thus become an object of fear to Herod, who at first sought to ignore him entirely by debarring him from the high priesthood, but his mother Alexandra Maccabeus (63 BCE – 28 BCE), through intercession with Cleopatra and Mark Antony, had compelled Herod to remove Hananel from the office of High Priest and appoint Aristobulus instead.

Herod, to secure himself against danger from Aristobulus, had instituted a system of espionage against him and his mother.

This surveillance proved so onerous that they sought to gain their freedom by taking refuge with Cleopatra.

As told by the Roman Jewish historian Josephus, their plans were betrayed and the disclosure had the effect of greatly increasing Herod's suspicions against his brother-in-law.

As Herod dares not resort to open violence, he causes him to be drowned while he is bathing in a pool in Jericho during a banquet organized by Aristobulus' mother.

Herod’s second wife, Mariamne I, has borne him two sons, Alexandros (b. 35 BCE) and Aristobulus (b. 31 BCE), and two daughters, Salampsio and Cypros.

Mariamne's father, Alexander of Judaea, the son of Aristobulus II, had married his cousin Alexandra, daughter of his uncle Hyrcanus II, in order to cement the line of inheritance from Hyrcanus and Aristobulus, but the inheritance had soon continued the blood feud of previous generations, and eventually led to the downfall of the Hasmonean line.

Mariamne, by virtue of her parents' union, claims Hasmonean royalty on both sides of her family lineage.

Josephus writes that it was because of Mariamne's vehement insistence that her husband, Herod, had made her brother, Aristobulos III, High Priest.

Within a year of his appointment, Aristobulos, who was not yet eighteen, had in 36 BCE drowned at a party in Jericho; Alexandra, his mother, blamed Herod.

Alexandra had written to Cleopatra, begging her assistance in avenging the boy's murder.

Cleopatra in turn had urged Mark Antony to punish Herod for the crime and Antony had sent for him to make his defense.

Herod left his young wife in the care of his uncle Joseph, along with the instructions that if Antony should kill him, Joseph should kill Mariamne.

Herod apparently believed his wife to be so beautiful that she would become engaged to another man after his death and that his great love for Mariamne prevented him from enduring a separation from her, even in death.

Joseph became familiar with the Queen and eventually divulged this information to her and the other women of the household, which did not have the hoped-for effect of proving Herod's devotion to his wife.

Rumors soon circulated that Herod had been killed by Antony, and Alexandra had persuaded Joseph to take Mariamne and her to the Roman legions for protection.

However, Herod was released by Antony and had returned home, only to be informed of Alexandra's plan by his mother and sister, Salome.

Salome also accused Mariamne of committing adultery with Joseph, a charge which Herod initially dismissed after discussing it with his wife.

After Herod forgave her, Mariamne inquired about the order given to Joseph to kill her should Herod be killed, and Herod then became convinced of her infidelity, saying that Joseph would only have confided that to her were the two of them intimate.

He gave orders for Joseph to be executed and for Alexandra to be confined, but did not punish his wife.

Herod, when visiting Octavian in 30 BCE in Rhodes to be confirmed as the Roman client-king of Judea, had separated Mariamne and Salome because of the conflict between the two, leaving his sister and his sons in Masada while moving his wife and mother-in-law, Alexandra, to Alexandrium.

Again, Herod had left instructions that should he die, the charge of the government was to be left to Salome and his sons, and Mariamne and her mother were to be killed.

Mariamne and Alexandra had been left in the charge of another man named Sohemus, and after gaining his trust again learned of the instructions Herod provided should harm befall him.

Mariamne became convinced that Herod did not truly love her and resented that he would not let her survive him.

Treating Herod coldly when he returned home, Mariamne had not concealed her hatred for him.

Salome and her mother had preyed on this opportunity, feeding Herod false information to fuel his dislike.

Herod still favored her, but she refused to have sexual relations with him and accused him of killing her grandfather, Hyrcanus II, and her brother Aristobulus.

Salome insinuated that Mariamne planned to poison Herod, and Herod had Mariamne's favorite eunuch tortured to learn more.

The eunuch knew nothing of a plot to poison the king, but confessed the only thing he did know: that Mariamne was dissatisfied with the king because of the orders given to Sohemus.

Herod, outraged, called for the immediate execution of Sohemus but permitted Mariamne to stand trial for the alleged murder plot.

Mariamne's mother, to gain favor with Herod, even implied Mariamne was plotting to commit lèse majesté.

Historians say her mother was next on Herod's list to be executed and did this only to save her own life.

Mariamne in 29 BCE is ultimately convicted and executed.

Herod for many months will grieve for Mariamne.

Herod executes his brother-in-law Kostobar (husband of Salome, father to Berenice) for conspiracy in 28 BCE.

Alexandra declares herself Queen, stating that Herod is mentally unfit to serve.

Josephus will write that this was Alexandra's strategic mistake; Herod executes her without trial.