According to the Old Testament, Jacob had twelve sons.
Genesis names the sons who become the ancestors of the twelve tribes of Israel. They are Reuben, Simeon, Levi, Judah, Dan, Naphtali, Gad, Asher, Issachar, Zebulun, Joseph, and Benjamin. Jacob is later given the name Israel, which explains the connection between his family and the tribes.
The family story involves Jacob’s wives Leah and Rachel and their servants Bilhah and Zilpah. Joseph’s two sons, Ephraim and Manasseh, later receive tribal status, which can make lists of the tribes appear to contain different combinations while preserving the traditional total of twelve.
A common source of confusion is that Jacob also has a daughter named Dinah, who is explicitly mentioned in Genesis. Thus, twelve sons does not mean Jacob had only twelve children. The number refers specifically to the sons who found the tribal lines.