The story of King Davis and Jonathan is an allegory. For Jonathan was the son of the King of Israel, King Saul of the tribe of Benjamin, the King chosen rule according to the Covenant made with Moses. David on the the other hand was a figure of the King of Promise, after the tribe of Judah.
Now even though Jonathan showed an extraordinary love towards his friend and brother, David, the promised King chosen and anointed of the Lord; In the end Jonathan's loyalty was to His Father, the King of the Old Covenant and the Law of Moses. That Kingdom of that House ended with the Death of King Saul and his son Jonathan.
The Kingdom then shifted from the house of Benjamin to the promised house of Judah and King David. That kingdom remained for two thousand years in different stages of exile and captivity, but that kingdom to came to an end as well when the inheritor of that Kingdom died, The SON of DAVID.
But through His death and resurrection, Christ has ascended to heaven where he rules the from New Jerusalem in the Kingdom of Heaven, from the new heavens to the new earth by His Spirit who dwells within us.
When the day of your decision comes Jonathan, and in spite of the obvious affection you have shown me, which Father will you choose? And to which which kingdom shall your loyalty lay? You should know that it is not required of you that you should go and fall up your own sword.