After Yaakov’s death, his sons were afraid Yosef would take revenge on them. (Remember, Eisav had said that when Yitzchak died, he would attack Yaakov.)
They sent a message to Yosef to say that Yaakov had wanted him to bear his brothers’ sins and not retaliate for selling him. Upon hearing this, Yosef began to cry.
Many opinions hold that Yaakov went to his grave not knowing what happened (a great lesson about curiosity in itself) and that he did not make such a request. Yosef’s tears, then, were because his brothers suspected he was so small of character that he would get even.
Perhaps, though, we can suggest that when the brothers said this, they were not making it up. Rather, they conveyed that from seeing how Yaakov lived his life, such as when Shechem kidnaped Dina, they understood his philosophy of forbearance and acceptance of what Hashem did to him through others.
They wanted Yosef to act in kind and not to take action for their wrongdoing.
In this case, the tears Yosef shed may have been because he was separated from his father for so many years and unable to learn the lessons he might have, simply from being in Yaakov’s presence. Yosef cried over the lost opportunity of Yaakov’s influence.
