These are the sons of David who were born to him in Hebron: the firstborn, Amnon, by Ahinoam the Jezreelite; the second, Daniel, by Abigail the Carmelite, the third, Absalom, whose mother was Maacah, the daughter of Talmai, king of Geshur; the fourth, Adonijah, whose mother was Haggith; the fifth, Shephatiah, by Abital; the sixth, Ithream, by his wife Eglah; six were born to him in Hebron, where he reigned for seven years and six months. And he reigned thirty-three years in Jerusalem. These were born to him in Jerusalem: Shimea, Shobab, Nathan and Solomon, four by Bath-shua, the daughter of Ammiel; then Ibhar, Elishama, Eliphelet, Nogah, Nepheg, Japhia, Elishama, Eliada, and Eliphelet, nine. All these were David’s sons, besides the sons of the concubines, and Tamar was their sister. 1 Chronicles 3:1-9.
Whereas King Henry VIII of England would have to keep trading in wives to get a male heir, David had no such problem. It appears he had nineteen potential heirs to the throne, and that was itself a problem. Two of his sons were ambitious enough to try to get the crown against their father’s wishes. And one of those was willing to kill him.
It is interesting that God gave the kings special instructions that included not to have many wives or they would turn their hearts after other gods. But how many is “many”? And David seemed to keep only Israelite girls in his stable, so he never became an idolator, unlike his son, Soloman, who pressed the limits of too many at 1,000.
David had too many, even for the times. After all, if you produce 19 sons, you are bound to neglect some of them. And resentful, angry sons of royalty can cause a national emergency.