Mephibosheth was 5 years old when news came of the death of his father and grandfather at the hand of the Philistines at the Battle of Mount Gilboa. His nurse tried to quickly flee with him, but dropped him causing him to be crippled.
After David defeated the House of Saul and had firmly set himself up as the king of all Israel, he questioned if there was still anyone left alive of the House of Saul. When he was told about Mephibosheth, son of Jonathan, he called him to his palace. There David reinstated to Mephibosheth all of the lands of Saul and assigned him servants to keep up the lands for him and also had him live in Jerusalem and eat at the table of the king. David had a great bond of friendship with Jonathan, and showed it through honoring his son.