Genesis 42:4

But Benjamin, Joseph's brother, Jacob sent not with his
brethren
Benjamin is called Joseph's brother, because he was so both by father and mother's side, as the rest were not; him Jacob kept with him, being the youngest and his darling, the only son he had with him of his beloved wife Rachel; and was very probably the more beloved by him since he had been bereft of Joseph; and it was not only to keep him company that he retained him at home, but for the reason following: for he said, lest peradventure mischief befall him;
as had to Joseph his brother, as he imagined; either that the journey would be too much for him, being young, or lest he should be seized with sickness on the road, or rather with death, as Aben Ezra interprets it according to the Targums of Onkelos and Jonathan.