2 Samuel 19:20 - Albert Barnes' Notes on the Bible

This is the first time that the “house of Joseph,” or “Joseph,” stands for all the ten tribes of which Ephraim was the head and leader. While Saul of Benjamin was king, or while Mahanaim was the capital of his son’s kingdom, it was not natural so to name them, nor does it seem so at first sight in the mouth of Shimei the Benjamite. But it is very possible that he used the phrase for the purpose of exculpating himself and his own tribe from having taken the initiative in the rebellion, anti of insinuating that they were drawn away by the preponderating influence of the great house of Joseph. On the other hand, the phrase may be an indication that the passage was written after the separation of the kingdom of Israel, when the phrase was a common one.