Genesis 42:11

We are all one man's sons - We do not belong to different tribes, and it is not likely that one family would make a hostile attempt upon a whole kingdom. This seems to be the very ground that Joseph took, viz., that they were persons belonging to different tribes. Against this particularly they set up their defense, asserting that they all belonged to one family; and it is on the proof of this that Joseph puts them, Genesis 42:15 , in obliging them to leave one as a hostage, and insisting on their bringing their remaining brother; so that he took exactly the same precautions to detect them as if he had had no acquaintance with them, and had every reason to be suspicious.