He certainly knew by the time he told David, "You are going to be the king of Israel, and I will be next to you" (1 Sam 23:17).
Jonathane o ne a raya Dafide a re: "O tla nna kgosi ya Iseraele, mme nna ke tla nna wa bobedi fa morago ga gago." - 1 Samuele 23:17