John Gill Commentary Genesis 37:16

"And he said, I am seeking my brethren: tell me, I pray thee, where they are feeding [the flock]." — Genesis 37:16 (ASV)

And he said, I seek my brethren
Whom, no doubt, he described to the man, and told him who they were, and to whom they belonged; or otherwise the man would have been at a loss to know who he meant, and what further to say to him, and without which Joseph would never have made the following request to him:

tell me, I pray you, where they feed [their flocks] ;
in what part of the country they are, what field they are in, how far to it, and which the way.