He was not jealous (1 Samuel 20)

So Jonathan made a solemn pact with David, saying, “May the LORD destroy all your enemies!” And Jonathan made David reaffirm his vow of friendship again, for Jonathan loved David as he loved himself.

Jonathan knew that David was the Lord’s anointed, and would soon be king over all Israel. And even though Jonathan was the king’s son, and heir to the throne, he was not jealous of David — he loved him unselfishly.