Joseph is the Christ within, the higher self that tends the flock of thoughts among the lower thoughts that surround it. The brethren are the left-side thoughts of a person, and they cannot abide the higher one moving among them. He carries their evil report up to the father, the right hemisphere of the brain, the higher seat where their nature is known for what it is.
So the inner Christ is set among the crowd of lesser thoughts and reports them truthfully to the higher mind, and for this the 12 turn on him and drive him out. The rupture that follows is not a family quarrel but the separating of the higher self from the old traditions and the lower crowd that resent its presence.
Joseph: the Christ within, the higher self among the thoughts
Brethren: the left-side thoughts of a person, the lower crowd
Father: the right hemisphere of the brain, the higher seat of knowing
Flock: the thoughts a person tends and watches over