Or HaChaim on Genesis 42:3/אור החיים על בראשית מ״ב:ג׳

1 אחי יוסף, Joseph's brothers. The reason they are described as Joseph's brothers instead of as Jacob's sons is that at that time they were determined to perform the brotherly act of redeeming him out of slavery.

2עשרה, ten. During famine, more than during any other time, people are extremely miserly and malevolent; they are apt to commit robbery and even murder to secure a piece of bread. This is why all the brothers went down to Egypt. If attacked, they could help one another. They also wanted to take Benjamin with them, but their father demurred. This is why the Torah makes a point of saying: "he did not send Benjamin." Had it not been for Jacob's concern that an accident would befall Benjamin he would have sent him along.

3Besides, it appears that Joseph was selling a fixed amount of grain to each purchaser. He had two objectives in mind, an obvious one and a secret one. The obvious objective was to prevent speculating in grain if someone were to purchase an amount larger than for his own needs. Joseph's method was of benefit both to him and to the purchasers. By refusing to sell large quantities at one time, Joseph could take advantage of any rise in price when it occurred. The customers benefited by what he did since Joseph did not raise prices unreasonably. Joseph's secret objective was to force each of the brothers to make a trip to Egypt to provision himself as he only sold rations for one family at a time.