According to Moses, this means that the person in charge said to the brothers that they couldn't come back and meet him unless they brought their younger brother with them. It's like when someone says, "I won't talk to you again unless you bring your little brother."
Genesis 44:23: And thou saidst unto thy servants, Except your youngest brother come down with you, ye shall see my face no more.
Contradicts Genesis 44:23 as it emphasizes bringing the brother down, contrasting with the condition set in Genesis 44:23 that he shall not see the father's face without the brother.
Genesis 44:21: And thou saidst unto thy servants, Bring him down unto me, that I may set mine eyes upon him.