For Jonathan's sake, whom did David invite to always eat at the king's table?

Answer: Mephibosheth

David restored Saul's land to Jonathan's son Mephibosheth, who was lame in both feet, and he always ate at the king's table.

“And when Mephibosheth son of Jonathan, the son of Saul, came to David, he fell facedown in reverence. Then David said, “Mephibosheth!” “I am your servant,” he replied.”— 2 Samuel 9:6 (BSB)