Genesis 42:10

Nay, my lord. If Joseph’s brothers were offended by the accusation hurled against them, fear led them to swallow their pride, and they asserted their complete innocence. When their claim to being honest men failed to impress the Egyptian lord, they told him more particularly about their family. By this they sought to prove their innocence. Inasmuch as they all belonged to one family, which could hardly make a hostile attack upon a whole kingdom, there was no real reason for suspecting them of being spies. Joseph took up the challenge and insisted that they prove the accuracy of their story by producing their missing youngest brother.