Mephibosheth was the son of Jonathan, and grandson of Saul. He was five years old when his father and grandfather fell in battle with the Philistines on Mount Gilboa. Hearing the news, Mephibosheth's nurse picked him up and fled, but as she hurried to leave, she dropped the child who injured his legs and became crippled for life.
Mephibosheth was raised by Makir at Lo-debar. Years later, after David had subdued all his adversaries and became undisputed king of all of Israel, he remembered a promise he had made to Jonathan, his best friend, that he would never cut off his kindness from his family.
David asked, "Is there anyone still left of the house of Saul to whom I can show kindness for Jonathan's sake?"
(2 Samuel 9:1)
When he found out about Mephibosheth, he asked that the man be brought to him. As Mephibosheth hobbled into the royal court he bowed low to mark his respect, undoubtedly certain that his last days had come. He was in for a surprise. Not only did David restore all this grandfather's lands to him, he welcomed him to dine at his own table.
A while later, though, when David was a fugitive, Mephibosheth didn't accompany him. Ziba, the same servant who had earlier informed David that Mephibosheth was alive, now slanderously misrepresented him to David, saying his nephew was unfaithful. According to Mephibosheth's own story, however, he had remained loyal to his king.
Mephibosheth, Saul's grandson, also went down to meet the king. He had not taken care of his feet or trimmed his mustache or washed his clothes from the day the king left until the day he returned safely. When he came from Jerusalem to meet the king, the king asked him, "Why didn't you go with me, Mephibosheth?" He said, "My lord the king, since I your servant am lame, I said, 'I will have my donkey saddled and will ride on it, so I can go with the king.' But Ziba my servant betrayed me.
(2 Samuel 19:24-26)
It is possible that David didn't entirely believe him, because he divided the estate he had given into two, giving the other half to Ziba, but he continued to protect Mephibosheth until the end of his days.