All Kings of the line of David had a "Queen Mother", who held a position of honor in the Israelite court. Her position was especially important because the King often himself had many wives-- while the wife of the Hebrew King was one of many, and not always in favor, the queen mother had a special influence in the court, and had the ear of the king.
"Say to the king and the queen mother: 'Take a lowly seat, for your beautiful crown has come down from your head.'" (Jeremiah 13:18)
"(This was after King Jehoiachin and the queen mother, the court officials and the leaders of Judah and Jerusalem, the skilled workers and the artisans had gone into exile from Jerusalem.)" (Jeremiah 29:2)
"Nebuchadnezzar took Jehoiachin captive to Babylon. He also took from Jerusalem to Babylon the king’s mother, his wives, his officials and the prominent people of the land." (2 Kings 24:15)
"So Bathsheba went to King Solomon to speak to him on behalf of Adonijah. And the king rose to meet her and bowed down to her. Then he sat on his throne and had a seat brought for the king's mother, and she sat on his right. Then she said, “I have one small request to make of you; do not refuse me.” And the king said to her, “Make your request, my mother, for I will not refuse you.” She said, “Let Abishag the Shunammite be given to Adonijah your brother as his wife.” King Solomon answered his mother, “And why do you ask Abishag the Shunammite for Adonijah? Ask for him the kingdom also, for he is my older brother, and on his side are Abiathar the priest and Joab the son of Zeruiah.” (1 Kings 2:19-22)
The Bible, in a prophecy from the mouth of King David, says that the Messiah shall have a Queen mother at His right hand:
"Kings’ daughters were among Thy honourable women: upon Thy right hand did stand the queen in gold of Ophir." (Psalm 45:9)
Jesus Christ is of the line of David; as such He is the Davidic King 'par excellence'. He is the fulfillment, the 'true King of Israel', of whom the previous Kings were imperfect foreshadowings of.
Who is Christ's Queen Mother? The answer is Mary. St. Luke mines this 'Queen Mother' imagery in the earliest parts of his Gospel:
"And Elizabeth was filled with the Holy Spirit, and she exclaimed with a loud cry, “Blessed are you among women, and blessed is the fruit of your womb! And why is this granted to me that the mother of my Lord should come to me?" (Luke 1:42-43)
"Mother of my Lord", coming from the mouth of a Jewish woman, is an obvious reference to such Old Testament imagery. Recall also that the Jewish authorities took Christ's claim to be 'Son of David' as a claim to kingship and a threat to Caesar.
St. John is not outdone in his descriptions of the exaltedness of Mary.
"And there appeared a great wonder in heaven; a woman clothed with the sun, and the moon under her feet, and upon her head a crown of twelve stars: and she being with child cried, travailing in birth, and pained to be delivered... And she brought forth a man child, who was to rule all nations with a rod of iron: and her child was caught up unto God, and to his throne." (Revelation 12:1-2,5)
As Christ is the 'Son of David', of the 'root of Jesse', so the Virgin Mary is the true 'Queen Mother', fulfilling the role for which God prepared her, for which she was raised, and that David prophesied. "Upon Thy right hand did stand the queen in gold of Ophir."