The rejection and choice of sons is a theme throughout the book of Breisheet. This principle may have guided the Yosef's brothers to reject him by selling him into slavery. Likewise, this principle may explain why Yosef never contacted his father – an understanding that he was the rejected son.

When his brothers come to Egypt, Yosef realizes that this is not the case. As his dreams told him, he must be a leader to his brothers: bring them to repent and reunite his shattered family.

Courtesy of Rabbi Menachem Leibtag www.tanach.org