Israelites, I need your help and clarifications, regarding the family of Aaron and David...!?

The role of Aaron's family (Moses, etc) was to be the leader in leading out the children of Israel from Egypt in Africa. Moses was from the tribe of Levi. They couldn't become Kings because the bloodline in which Jesus Christ the son of GOD came from the king line; which is Judah. David is of the seed of Abraham- they are brethren. David is a descendant of Boaz, Jesse, Nahshon, Perez, etc Yes! The kingship was given to the Tribe of Judah from GOD. Judah was the fourth son born to Jacob/Israel and he became the king of all his brothers.