'Families' in the Bible

You are the sons of the prophets and of the covenant that God made with your ancestors, saying to Abraham, And all the families of the earth will be blessed through your offspring.

And he made with him the agreement of which circumcision was the sign. And so Abraham had a son, Isaac, and gave him circumcision on the eighth day; and Isaac had a son, Jacob, and Jacob was the father of the twelve heads of the families of Israel.