Israel had 12 sons, as follows:
Reuben, Simeon, Levi, Judah, Dan, Naphtali, Gad, Asher, Issachar, Zebulun, Joseph, and Benjamin. (Jacob was renamed Israel Gen. 32:27-29)
The Tribe of Levi was set apart from the others in the sense that, the members of the Tribe of Levi were to be in charge of the tabernacle of the Testimony. (see: Num. 1).
The Tribe of Joseph is not usually listed with the Hebrew tribes although Joseph is one of Jacobs twelve sons, the eldest of Rachel. It is sometimes referred to as the House of Joseph. Rather, the two tribes founded by his sons Ephraim and Manasseh are listed separately.
Tribal Divisions
Politically, the Israelites were composed of thirteen tribes: Reuben, Simeon, Levi, Judah, Dan, Naphtali, Gad, Asher, Issachar, Zebulun, Manasseh, Ephraim, and Benjamin. In parts of the Bible, Ephraim and Manasseh are treated as together constituting the House of Joseph, while the Levi have a special religious role and had only scattered cities as territory; whence traditionally either Ephraim and Manasseh were counted as one tribe, or Levi wasn't counted, so that together the tribes were the Twelve Tribes of Israel.
The division into Tribes was geographical, as well as genealogical; each tribe held a distinct territory, though there are a few peculiarities. Levi's territory was very discontinuous, consisting entirely of towns and cities scattered as enclaves within the territory of the other tribes, Simeon's territory was entirely inside the territory of Judah, and Manasseh was split between the half tribe west of the Jordan, and the other half tribe on the eastern side. The Kingdom of Judah consisted of Judah, Simeon, Benjamin, and the parts of Levi within those lands, while the Kingdom of Israel contained Reuben, Dan, Naphtali, Gad, Asher, Issachar, Zebulun, Manasseh, Ephraim, and the remainder of Levi.
More...