The first part of parshas Vayeshev deals with a very troubling story well known to all, the selling of Yosef haTzadik by his brothers into slavery. Reams and reams of interpretations have been written on this but i would like to add my little bit.
The parasha starts off by telling us Yosef was a na'ar, a youth. However, it also tells us he was seventeen years old. Now, this is in itself curious for a couple of reasons. First of all, according to the Torah's chronology of events, the first eleven brothers, from Reuven to Yosef, were all born within six years of each other. So although the Torah may have considered Yosef a youth, the majority of the brothers were not much older than him. Why is he specified as being so young?
Then there is the obvious contradiction - Yosef is 17 years old. Now, in today's society that's young but back then people were getting married and having kids by that age, as the Gemara proves in Sanhedrin from several places througout Nach. So he wasn't necessarily so young either. What is the verse trying to tell us?
Additionally, we have to look at the reason for why the brothers sold Yosef in the first place. the text seems pretty clear that they felt threatened by Yosef's dreams of rulership over them. Yet why should this be so? After all, did they expect the future B'nai Yisrael not have any ruling structure?
Rav Yehudah Zvi Kook notes that the 12 brothers represent all possible facets of the future nation. That is, each brother had unique characteristics allowing him to endow a future role to the nation of Israel in general. Yes, there was variety but in the same way a diamond might have several facets yet it remains one stone, so each tribe through its unique characteristics would form an essential part of the nation.
Amongst the others, it was the role of Yehudah to be the king of the nation, as is clear from both Moshe Rabeinu's and Yaakov Avinu's brachos to the brothers/tribes. Yet in the context of the facets concept noted, this puts the Jewish idea of leadership into a new focus. Yes Yehudah was to be the leader was leadership, just like artisanship, learning, or business acumen, is a facet of the nation, not a quality putting the tribe above the rest. Leadership is a burden, a task and public service, not a position of lordship in Jewish thought.
(Even though one might object by pointing out all the special things a king gets that seem to be above the law, the response to that is to remember that the royal office requires dignity and respect. These laws are designed to remind people of the importance of the king. Yet at all times he remains within the law, unable to change halachah and just as responsible to it as the lower person on the social ladder)
It is possibly for this reason that the brothers were angered by Yosef's dreams. As opposed to the role of leadership envisioned for Yehudah, Yosef's dreams implied that he viewed himself as leader, which contradicted the accepted roles in the family, and that his idea of ruling was to be above the brothers, with them all bowing at his feet and accepting his superiority over them. This was incompatible with what they saw as the future structure of the nation. Thus the harsh opposition it raised.
This can also explain the reason for the redundancy in the verse mentioned at the beginning of the post. Na'ar does not only mean "youth" but also to stir up. I wonder if there is a relationship between the two, youth being the time when new emotions stir up within a person. Regardless, one can look at the verse as an implied criticism of Yosef. Working together, the nation advances and grows with each tribe playing its assigned role and recognizing its subsidiary part to the whole. And along comes Yosef, with the idea of changing the paradagm, hencing stirring up that which should have been settled. But at the age of 17, he should have known better. This would be how i would understand the opening verses of the parashah.