Jamieson, Fausset and Brown on Genesis 37:2

2. generations--leading occurrences, in the domestic history of Jacob, as shown in the narrative about to be commenced.

Joseph ... was feeding the flock--literally, "Joseph being seventeen years old was a shepherd over the flock"--he a lad, with the sons of Bilhah and Zilpah. Oversight or superintendence is evidently implied. This post of chief shepherd in the party might be assigned him either from his being the son of a principal wife or from his own superior qualities of character; and if invested with this office, he acted not as a gossiping telltale, but as a "faithful steward" in reporting the scandalous conduct of his brethren.