Then Joseph could not restrain himself before all those who stood by him; and he cried, "Cause every man to go out from me!" And there stood no man with him while Joseph made himself known unto his brethren. And he wept aloud, and the Egyptians and the house of Pharaoh heard. And Joseph said unto his brethren, "I am Joseph. Doth my father yet live?" And his brethren could not answer him, for they were troubled at his presence (Genesis 45:1 - 3 KJV)
Nahmanides phrases the question eloquently:
"How is it that Joseph, after living many years in Egypt, having attained a high and influential position in the house of an important Egyptian official, did not send his father even one message to inform him (that he was alive) and comfort him? Egypt is only six days' travel from Hebron, and respect for his father would have justified even a year's journey! (Commenting on Gen. 42:9)?"
So...why didn't Joseph ever try to contact his father?
Some of my own thoughts on this question, to offer a concrete direction for inquiry.
In Genesis 13, Abraham separates from his nephew Lot. At that moment, Lot is excluded from the covenantal relationship that God forges with Abraham and his offspring. In Genesis 25, Abraham rejects the children of his concubines, including Ishmael, and excludes them from the covenantal relationship which he bequeaths to Isaac. Genesis 27 - Isaac's son Esau is excluded from the covenant in a dramatic tale which includes Jacob stealing a blessing from his blind father. Jacob's earlier stealing of the birthright in chapter 25 suggests that the siblings understood they were in competition - one of the two might not be included in the Abrahamic covenant. This familial tension may be useful in trying to understand the hatred that Joseph's brothers harbored toward Joseph and their desire to kill him:
Now Israel loved Joseph more than all his children, because he was the son of his old age; and he made him a coat of many colors. And when his brethren saw that their father loved him more than all his brethren, they hated him and could not speak peaceably unto him. And Joseph dreamed a dream, and he told it to his brethren; and they hated him yet the more (Genesis 37:3-5 KJV).
How does the lack of communication between Joseph in Egypt and his father play into this larger family dynamic? How does the unfolding of the Joseph story play with and twist assumptions held by Joseph, his brothers and the reader as the story progresses?