You are my brothers, my own flesh and blood. So why should you be the last to restore the king?’
He reminds Judah that they are his brothers and his own flesh and blood.
It grounds the appeal in kinship and shared identity.
8So the king got up and sat in the gate, and all the people were told: “Behold, the king is sitting in the gate.” So they all came before the king. 9Meanwhile, the Israelites had fled, each man to his home. And all the people throughout the tribes of Israel were arguing, “The king rescued us from the hand of our enemies and delivered us from the hand of the Philistines, but now he has fled the land because of Absalom. 10But Absalom, the man we anointed over us, has died in battle. So why do you say nothing about restoring the king?” 11Then King David sent this message to Zadok and Abiathar, the priests: “Say to the elders of Judah, ‘Why should you be the last to restore the king to his palace, since the talk of all Israel has reached the king at his quarters? 12You are my brothers, my own flesh and blood. So why should you be the last to restore the king?’ 13And say to Amasa, ‘Aren’t you my flesh and blood? May God punish me, and ever so severely, if from now on you are not the commander of my army in place of Joab!’” 14So he swayed the hearts of all the men of Judah as though they were one man, and they sent word to the king: “Return, you and all your servants.” 15So the king returned, and when he arrived at the Jordan, the men of Judah came to Gilgal to meet him and escort him across the Jordan.