The Virgin Mary with a spindle. The Gospel of Pseudo-Matthew describes how Mary and the other Temple virgins were spinning purple thread in the Women's compound when the Angel Gabriel appeared to her.
Cousin brides played a significant role in the building up of the early Hebrew clans. There are numerous references to cousin brides in the Bible. Keturah was Abraham's patrilineal cousin. ("Patrilineal" means they have a common male ancestor.) Zipporah was Moses's patrilineal cousin, and Hannah was Elkanah's cousin. The Virgin Mary was Joseph's cousin bride.
Lamech’s daughter Naamah (Gen. 4) married her patrilineal cousin Methuselah (Gen. 5) and named their first-born son Lamech after her father. This is called the "cousin bride's naming prerogative". The cousin-bride’s naming prerogative is a distinctive feature of the marriage and ascendancy pattern of the biblical Hebrew. This custom necessitates speaking of two different individuals named Lamech: Lamech the Elder and Lamech the Younger.
Typically, high ranking Hebrew rulers had two wives. The wives resided in separate settlements that marked the ruler's territorial boundaries. The Hebrew ruler-priest was wedded to his first wife while he was still young, probably around the age 18. His second wife was taken as he approached ascendancy to rule over his father’s territory, probably no younger than 40. This means that the children born to the first wife were considerably older than the children born to the second wife.
Sarah and Abraham were married while they still lived in the territory of their father Terah. Sarah’s barren state delayed the birth of Abraham’s proper heir, Isaac. This meant that the children born to Keturah were older than Isaac. However, none of the six sons born to Keturah (Gen. 25) were regarded as Abraham’s proper heir according to the marriage and ascendancy pattern of the early Hebrew. The proper heir was the first-born son of the first wife.
The first wife was usually as half-sister, as was Sarah to Abraham (Gen. 20:1-16). This was the bride of the man's youth. The first-born son of this wife was the man’s proper heir. As the heir approached ascendancy to his father's territory, he took a second wife. Typically, this bride was a patrilineal cousin, as was Rebekah to Isaac.
It appears that two wives were an essential part of establishing and maintaining territorial boundaries among royal persons. That this practice pertained to exceptionally high-status persons is evident in that the pattern is associated only with rulers such as Abraham, or ruling families such as that of Jesse, the father of King David and the grandfather of King Solomon.
Consider the Song of Songs which speaks of two royal brides. One bride is described as “dark as the tents of Kedar” (1:5) and the other is described as “fair as the moon” (6:10). This is typical of the territorial claims of high kings in the Ancient Near East. The brides represent the east and the west, the territorial boundaries observed by the solar arc, the symbol of the God’s High rule over the Earth. This was a way of identifying the authority of the high king with the authority of the High God.
The names of Lamech’s two wives Adah and Tzillah are another example. Theodore H. Gaster noted that the east-west arrangement is suggested by the names Adah (dawn) and Tzillah (dusk).
The Importance of the Cousin Brides
The ascendant ruler’s second wife was a patrilineal cousin. This marriage came much later than the first marriage to the half-sister bride. This explains Abraham’s urgency, as he faced death, that a cousin bride should be found for Isaac (Gen. 24). Isaac’s marriage to Rebekah would have come late in his life. The bride of his youth would have been a half-sister, the daughter of Abraham and Keturah.
The Bible does not identify Isaac’s first wife. Her presence is suggested by the fact that Isaac was living near Beersheba when Abraham’s servant arrived from Padan-Aram with Rebekah. Beersheba was where Keturah resided with her children.
It has been noted that the twin boys assigned to Rebekah may have been the first-born sons of Isaac’s two wives. This aligns with the social structure of the early Hebrew. Since Esau was Isaac’s proper heir, he would have been the first-born son of Isaac and his half-sister bride. Rebekah would be the mother of Jacob, a sent-away son. This also aligns with the social structure of the early Hebrew, as the son of the cousin bride belonged to the household of his maternal grandfather and would reside there after coming of age. This occurred with Jacob who went to live with his maternal uncle (avuncular residence).
Related reading: The Hierarchy of Hebrew Sons; Terah's Two Wives; Royal Sons and Their Maternal Uncles; Hebrew Rulers with Two Wives; Sovereignty and Two Wives