Moshe is instructed by Hashem to take a census of Bnei Israel. Everyone was to be counted LEMISHPECHOTAM, “…according to their families…”.(Num. 1,2) Rashi explains that this means everyone was to identify himself according to his tribe. In Hebrew we call this YICHUS or genealogy. The intention here is that we should know whence we stem.
The Jewish people recognize that we are descendants of our forefathers, Avraham, Yitzchak and Yaakov. Lest we forget, other nations of the world also descend from these Patriarchs. The descendants of Ishmael also came from Avraham and the descendants of Esav also came from Yitzchak. What then is the difference between them and us?
The difference stems from how one looks at his Yichus. They look at their forefathers with pride in that they come from great people and hence are themselves worthy by reason of birth. We look at our Patriarchs with awe and responsibility in that we have to imitate their wonderful traits and have to earn our own merit.
This explains the Midrash which tells us that the nations of the world complained about why the Jews deserve the Torah more than they. They have the same worthy ancestors. The answer is that they look at their ancestors as a source of pride. The Jews look at them as a source of responsibility to follow their life style and continue in their footsteps.