Copper coin of Herod, bearing the legend "ΒΑΣΙΛΕΩΣ ΗΡΩΔΟΥ" ("Basileōs
Hērōdou") on the obverse
It is generally accepted that Herod was born around 73 BCE in Idumea, south of Judea.. However, some authors think that he was born in about 72/71 BCE. He was the second son of Antipater the Idumaean, a high-ranking official under ethnarch Hyrcanus II, and Cypros, a Nabatean. Herod's father was by descent an Edomite, descendants of Esau, whose ancestors had converted to Judaism. Herod was raised as a Jew.
A loyal supporter of Hyrcanus II, Antipater appointed his son Herod governor of Galilee in 47 BCE, when Herod was about either 25 or 28 years old. His elder brother, Phasael, was appointed governor of Jerusalem. Herod enjoyed the backing of Rome, but his brutality was condemned by the Sanhedrin.
In 41 BCE, Herod and his brother Phasael were named as tetrarchs by the Roman leader Mark Antony. They were placed in this role to support Hyrcanus II. Later, Antigonus, Hyrcanus' nephew, took the throne from his uncle with the help of the Parthians. Herod fled to Rome to plead with the Romans to restore Hyrcanus II to power. The Romans had a special interest in Judea because their general Pompey the Great had conquered Jerusalem in 63 BCE, thus placing the region in the Roman sphere of influence. In Rome, Herod was unexpectedly appointed King of the Jews by the Roman Senate. Josephus puts this in the year of the consulship of Calvinus and
Pollio (40 BCE), but Appian places it in 39 BCE. Herod went back to Judea to win his kingdom from Antigonus. Toward the end of the campaign against Antigonus, Herod married the granddaughter of Hyrcanus II, Mariamne (known as Mariamne I), who was also a niece of Antigonus. Herod did this in an attempt to secure his claim to the throne and gain some Jewish favor. However, Herod already had a wife, Doris, and a young son, Antipater, and chose therefore to banish Doris and her child.
After three years of conflict, Herod and the Romans finally captured Jerusalem and Herod sent Antigonus for execution to Marc Antony. Herod took the role as sole ruler of Judea and the title of basileus (Βασιλεύς, "king") for himself, ushering in the Herodian Dynasty and ending the Hasmonean Dynasty. Josephus reports this as being in the year of the consulship of Agrippa and Gallus (37 BCE), but also says that it was exactly 27 years after Jerusalem fell to Pompey, which would indicate 36 BCE. Cassius Dio also reports that in 37 BCE "the Romans accomplished nothing worthy of note" in the area. According to Josephus, Herod ruled for 37 years, 34 of them after capturing Jerusalem.
As some believe Herod's family were converts to Judaism, his religious commitment was questioned by some elements of Jewish society. When John Hyrcanus conquered the region of Idumaea (the Edom of the Hebrew Bible) in 140–130 BCE, he required all Idumaeans to obey Jewish law or to leave; most Idumaeans thus converted to Judaism, which meant that they had to be circumcised, and many had intermarried with the Jews and adopted their customs. While Herod publicly identified himself as a Jew and was considered as such by some, this religious identification was undermined by the decadent lifestyle of the Herodians, which would have earned them the antipathy of observant Jews.
Herod later executed several members of his own family, including his wife Mariamne I.