Humility and Repentance

Genesis 50:18 And his brethren also went and fell down before his face; and they said, Behold, we be thy ^aservants.

So, the whole reason why Joseph is in Egypt and ultimately the reason why Egypt became such a great nation and why Israel and his children and their families were spared because Joseph was sold into Egypt. He became a mighty ruler, and even though Joseph knew what had happened, he stayed humble and faithful the entire time.

Now his brothers realize that they have done an evil. I do not think that they are sorry because of what Joseph has done for them, but they to me seem humble and have repented because they love Joseph. There is an element that they realize that they are at the feet of Joseph's mercy which is why they said we be thy servant. This is could be their realization of the dreams that Joseph had. 

But more importantly than this family dynamics, with the Atonement of Christ, all can be forgiven, and we each have the capacity to forgive everyone who has wronged us.