Saul said to David, Behold, my elder daughter Merab, her will I give you as wife: only be valiant for me, and fight Yahweh's battles. For Saul said, Don't let my hand be on him, but let the hand of the Philistines be on him.
At any rate, Merab was given to Adriel instead of to David.  The Bible records the tragic story of the unhappy death of the sons of Merab and Adriel in  2 Samuel 21:8.