Holy Bible Online 
Maybe the right question should be: WHO Were the 12 tribes of Israel? The twelve sons of Jacob, who formed the twelve tribes of Israel, are:
Reuben, Simeon, Levi, Judah, Dan, Naphtali, Gad, Asher, Issachar, Zebulun, Joseph, and Benjamin (listed by birth order according to Genesis 29:32-35; 30:1-13, 17-24).
At the end of Jacob's life, while in Egypt, he "adopted" Joseph's sons, Ephraim and Manasseh, as his own (Genesis 48:5). This led to the tribe of Joseph splitting into two, and for over 400 years, Israel had 13 tribes. This arrangement remained until Israel's exodus from Egypt.
After the Exodus and before entering Canaan, God instructed that the tribe of Levi be set apart to assist the priest Aaron and his sons in the ministry of the tabernacle (Numbers 1:47-53; 3:5-9). The Levites were consecrated to God in place of the firstborn (Numbers 3:11-13; 8:14-19). At this point, the tribe of Levi was no longer counted as a tribe for inheritance purposes, bringing Israel back to twelve tribes.
The tribes that received land allotments when Israel entered Canaan were: Reuben, Simeon, Judah, Dan, Naphtali, Gad, Asher, Issachar, Zebulun, Ephraim, Manasseh, and Benjamin (Joshua 13:14-19:51). The Levites received only cities to inhabit among the other tribes.
Jacob had two wives, Leah and Rachel, and two concubines, Bilhah (Leah's maid) and Zilpah (Rachel's maid). With them, Jacob had twelve sons and one daughter named Dinah (Genesis 30:21).
Reuben
Reuben was Jacob's first son. The Bible says that Jacob loved Rachel more than Leah (Genesis 29:30). The Lord saw that Leah was unloved, and He made her fruitful. However, Rachel was barren (Genesis 29:31). Leah, upon giving birth to Jacob's first son, declared that God had seen her affliction.
Meaning: "Behold, a son." "Reuben" derives from the Hebrew word "reê," which means "see."
Leah became pregnant and gave birth to a son. She named him Reuben, for she said, “It is because the Lord has seen my misery. Surely my husband will love me now.”
- Genesis 29:32
Simeon
Simeon was Jacob's second son with Leah. Again, Leah attributed her ability to bear children to God and stated that He heard her cry.
Meaning: "Hearing." "Simeon" comes from the Hebrew root "shamá," which means "heard."
She conceived again, and when she gave birth to a son she said, “Because the Lord heard that I am not loved, he gave me this one too.” So she named him Simeon.
- Genesis 29:33
Levi
When Leah gave birth to Jacob's third son, she believed that her husband would be attached to her this time.
Meaning: "Attached." "Levi" is a Hebrew term derived from "liva," which means "joined."
Again she conceived, and when she gave birth to a son she said, “Now at last my husband will become attached to me, because I have borne him three sons.” So he was named Levi.
- Genesis 29:34
Judah
When Leah gave birth to her fourth son, this time she decided only to praise the Lord.
Meaning: "Praise." "Judah" comes from the Hebrew root "hodaá," which means "praise."
She conceived again, and when she gave birth to a son she said, “This time I will praise the Lord.” So she named him Judah. Then she stopped having children.
- Genesis 29:35
Dan
When Rachel saw that she was not bearing children, she became jealous of her sister. Then, following the custom of the time, which allowed a wife who could not bear children to give her maid to her husband to have children through her (Genesis 30:1-3), Rachel gave Bilhah to Jacob. Bilhah bore Jacob's fifth son. Rachel believed that God had vindicated her and named the boy "Dan."
Meaning: "Judge."
and she became pregnant and bore him a son. Then Rachel said, “God has vindicated me; he has listened to my plea and given me a son.” Because of this she named him Dan.
- Genesis 30:5-6
Naphtali
Bilhah, Rachel's maid, bore Jacob's sixth son. Rachel, feeling that she was in a competition and struggle with her sister, named him "Naphtali."
Meaning: "Wrestling."
Rachel’s servant Bilhah conceived again and bore Jacob a second son. 8 Then Rachel said, “I have had a great struggle with my sister, and I have won.” So she named him Naphtali.
- Genesis 30:7-8
Gad
When Leah saw that she had stopped bearing children, she made the same decision as her sister and gave her maid Zilpah to Jacob as a wife. Zilpah bore Jacob's seventh son, who was named "Gad." Leah named him this because she considered herself a fortunate woman.
Meaning: "Fortune."
Leah’s servant Zilpah bore Jacob a son. 11 Then Leah said, “What good fortune!”[a] So she named him Gad.
- Genesis 30:10-11
Asher
Zilpah, Leah's maid, bore Jacob's eighth son. Leah believed this would be the reason for her happiness. Therefore, she named him "Asher."
Meaning: "Happy."
Leah’s servant Zilpah bore Jacob a second son. Then Leah said, “How happy I am! The women will call me happy.” So she named him Asher.
- Genesis 30:12-13
Issachar
Leah conceived again and bore another son, her fifth with Jacob (the ninth son of Jacob, including the sons of the maids). Leah understood that God was rewarding her, so she named him "Issachar."
Meaning: "Reward." "Issachar" comes from the Hebrew word "sachar," which means "reward."
God listened to Leah, and she became pregnant and bore Jacob a fifth son. Then Leah said, “God has rewarded me for giving my servant to my husband.” So she named him Issachar.
- Genesis 30:17-18
Zebulun
Leah became pregnant again and bore her sixth son with Jacob (the tenth son of Jacob, including the sons of the maids). Because she had borne so many sons, she believed that now her husband would dwell with her.
Meaning: "Dwelling." "Zebulun" derives from the Hebrew word "zevul," which means "dwelling place."
Leah conceived again and bore Jacob a sixth son. Then Leah said, “God has presented me with a precious gift. This time my husband will treat me with honor, because I have borne him six sons.” So she named him Zebulun.
- Genesis 30:19-20
Joseph
Finally, Rachel conceived and bore a son. The biblical text states that the Lord remembered Rachel. This shows a direct intervention from the Lord. He is Rachel's first son, but he is Jacob's eleventh son. Rachel named him Joseph, hoping that God would add another son to her.
Meaning: "He who adds."
Then God remembered Rachel; he listened to her and enabled her to conceive. She became pregnant and gave birth to a son and said, “God has taken away my disgrace.” She named him Joseph,and said, “May the Lord add to me another son.”
- Genesis 30:22-24
Read and learn more about the story of Joseph in Egypt (son of Jacob).
Manasseh
Joseph, still young, had been sold by his brothers as a slave to a caravan of Ishmaelites going to Egypt (Genesis 37:3-28). Manasseh was born in Egypt after Joseph was released from prison and had become governor of Egypt (Genesis 41:1-50). Manasseh is Joseph's firstborn son, who was later "adopted" by Jacob (Genesis 48:5). Joseph named his son this because God had made him forget his affliction.
Meaning: "Causing to forget."
Joseph named his firstborn Manassehand said, “It is because God has made me forget all my trouble and all my father’s household.”
- Genesis 41:51
Ephraim
Ephraim is Joseph's second son in Egypt. He named him this because he was his second son and because this son was born during the seven years of abundance in Egypt. This period of abundance produced enough to save thousands of lives during the seven years of famine that followed. With this, Joseph was saying that God had made him fruitful in the land of his affliction. He believed he was doubly fruitful.
Meaning: "Double fruit."
The second son he named Ephraim and said, “It is because God has made me fruitful in the land of my suffering.”
- Genesis 41:52
Benjamin
Rachel died giving birth to her second son. Before she died, she named him Benoni, which means "son of my sorrow." However, Jacob named him Benjamin ("Son of the right hand"), symbolizing that this son would be at his right hand, in a position of honor, as someone he loved.
Meaning: "Son of my right hand."
Then they moved on from Bethel. While they were still some distance from Ephrath, Rachel began to give birth and had great difficulty. And as she was having great difficulty in childbirth, the midwife said to her, “Don’t despair, for you have another son.” As she breathed her last - for she was dying - she named her son Ben-Oni. But his father named him Benjamin.
- Genesis 35:16-18
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