What does Genesis 42:13 mean?
Joseph has accused his ten older brothers of coming to Egypt as spies of some foreign power. They have truthfully insisted they are all the sons of one man sent to buy food for their people (Genesis 42:1–5). They don't realize that Joseph is their once-hated brother (Genesis 37:28), and that despite his anger (Genesis 42:7), he has no intent of harming them.Now they continue to provide details about their lives. Their intent is to explain how little they have in common with spies by describing the specifics of their ordinary lives. They repeat that they are all the sons of one man living in Canaan (Genesis 37:1). In addition, they mention, their youngest brother is back home with their father. The twelfth son they mention is Joseph himself; he is the one their father believes is dead (Genesis 37:31–34). It was fear of losing another son which led Jacob to keep Benjamin, the youngest, at home.
By backing his brothers into a corner, Joseph has provoked them to tell him information he must have longed to hear. He now knows his father Jacob and brother Benjamin are both still alive. He also has a clue as to how they explained his disappearance: lying to say that he is "no more."