Joseph, despite his high position in Egypt, did not even once attempt to contact his father.  Did he no longer care for his father who loved him so dearly and was still grieving for him?

Let's look at the "selection process" - the theme of the book of Genesis- in the story of Joseph and his brothers. 

"The Brothers' Hatred"

To understand the reason behind the brothers' hatred of Joseph, let's review the story of Joseph's dreams.

1.  "And behold we were gathering sheaves in the field, and my sheaf stood up and remained upright; then your sheaves gathered around and bowed down to my sheaf."  (Gen 37:7) 

2.  "And behold - the sun, the moon, and eleven stars were bowing down to me."  (Gen 37:9) 

Clearly, these dreams reveal Joseph's sense of superiority over his entire family.  They also echo an earlier sibling rivalry - between Jacob and Esau, over the blessing that Isaac gave to Jacob, though it was intended for Esau.

"May YHVH bless you with ... an abundance of grain... Be master over your brothers, and let your mother's sons bow down to you."  (Gen 27:28-29) 

This parallel suggests that Joseph's dreams were not only pointing to his future leadership position, but also to his 'election' as the only 'chosen son,' just as Jacob himself emerged as Isaac's only chosen son!
Jacob's love and special treatment of Joseph.  (Gen 37:3) 
Joseph's special coat, a sign of royalty.
Joseph being the first son of Rachel, Jacob's 'primary' wife. 
Jacob's silence regarding Joseph's dreams.  (Gen 37:11)

The conclusion was obvious. Jacob planned to name Joseph (or possibly Joseph and Benjamin) his exclusive heir(s).  Joseph's dreams simply added 'fuel to the fire!'

This very likely was the basis for the brothers' decision to kill Joseph.

Had Joseph been a bit more righteous in his brothers' eyes, they may have conceded to his destiny as either the 'leader' or the 'chosen' son. However, their perception of Joseph's character troubled them.  In their eyes, he was a slanderer.

"And Joseph brought bad reports of his brothers to his father."   (Gen 37:2) 

The brothers, aware of the challenges facing YHVH's special Nation, recognized the need for exemplary leadership.  Could Joseph possibly assume this role?  To the brothers, the mere thought of 'Joseph the Slanderer' becoming the leader of YHVH  'holy nation'.was unthinkable. 

The brothers faced a predicament similar to that of Rebekah's in the previous generation.  Just as Rebekah had realized that Isaac was mistaken in his favoring of Esau, so too the brothers realized Jacob's mistake in favoring Joseph.  Just as Rebekah resorted to 'trickery' to ensure that the 'proper' son would be blessed, so too the brothers decide to use 'trickery' to ensure that Joseph would not be appointed their leader.  Considering that the entire destiny of Israel was at stake, the brothers allowed themselves to 'bend the rules' a bit, so as to secure the nation's future.

An ideal opportunity arose when Joseph arrived at Dothan to visit his brothers.  In order to dispose of Joseph, they plotted first to kill him.  Later they opted to sell him off to a distant land.  In either case, their stated goal was to make sure that he was removed from the Divine family.  (Gen 37:20)  Out of respect and concern for their father, lest he worry about his 'missing' son for the rest of his life, they dipped his coat in blood so that Jacob would think that he was truly dead.  Hopefully, their father will finally realize that Joseph was 'rejected', and Israel will continue to develop in the proper fashion.  Thus, it was not only out of  jealousy that they wanted to kill him, but also out of a 'sincere' concern for the future of the 'nation of Israel'.

 Why Didn't Joseph Write Home?

Considering Joseph's relationship with his father (Gen 37:3) we would expect him to have made every possible attempt to contact his father.  Yet, even after his appointment as head servant of the House of Potiphar, Joseph made no effort to inform his father that he was alive and well.   Surely, after his appointment as the Commissioner of Egypt, second only to Pharaoh, he should have no problem whatsoever contacting his father.  Nevertheless, Joseph didn't seem to bother.  It appears as though he had completely wiped his past from his memory.

Was this done to ensure the fulfillment of his dreams?  
Would Joseph cause such suffering to his father simply because of a dream?  Or did Joseph understand that in order for the Divine plan to unfold, he must not contact his family? 
Was he attempting to bring his brothers towards repentance?  Why didn't he contact his father before they arrived in Egypt?

It is possible that Joseph was waiting for his father (and/or his brothers) to come to his rescue.  Surely, Joseph hoped, his father would find out that he was sold and demand that the brothers trace the sale and then go to Egypt to buy him back.  However, many months passed and no one came.  Joseph's hopes were replaced by a feeling of rejection.  After awhile, he reached the conclusion that he must have been 'rejected' from the 'election' process and accepted his new fate, thinking he was no longer wanted by his family.

Joseph's Mistaken Theory 

At age 17, full of energy, emotion and ambition, Joseph was sent by his father to check on his brothers.  As soon as they saw him, they immediately took off his coat and threw him into a pit.  A short time later, a group of Midianites removed him from the pit and sold him to a caravan of Ishmaelites.  His conclusion -  his brothers were either playing a trick on him, or even sold him into slavery.  Remember that Joseph didn't hear the brothers' original plan to kill him. Most likely, he expected his father will investigate the matter and find him by tracing the sale to Egypt.  Joseph was totally unaware that the brothers had tricked their father with the blood-stained coat into believing that he was dead.

The months passed, and nothing happened. Joseph no doubt was begining to wonder why no one came to look for him.  Did his father no longer care about him?  Why did the brothers throw him into the pit?  Why did his father send him out alone on such a long journey to see his brothers who hated him?  Slowly, he came to the realization that Jacob must have received some divine revelation that he was rejected, and only Leah's children, and not Rachel's had been 'chosen.'  Rachel, as her premature death may have indicated, had not attained the same status as Sarah and Rebekah...

It could be that Joseph, after many years of pondering these events,  concluded that his father had actually sent him knowing that the brothers would sell him, rather than telling him directly the terrible news of his 'rejection' from the family.  Or maybe his brothers convinced their father that Joseph's disappearance was a Divine indication of his rejection.

No doubt, 17 year old Joseph felt 'rejected' and 'abandoned' by his family.  Despite his father's love for him, he chose to begin a new life, even if it meant that his father would miss him, rather than face returning to live with his brothers.

Just as Esau established Edom, he would make a name for himself in Egypt and even bring the name of YHVH into that society.    

This may explain why Joseph, even after rising to power, never contacted his family.

All this suddenly changed twenty years later as Joseph recognized his brothers when they came to Egypt to buy grain.  As they bowed down before him, he suddenly remembered his long forgotten dreams. Should he dismiss this as pure coincidence, or should this partial fulfillment of his childhood dreams lead him to reconsider his earlier conclusions?

Joseph's Plan

Joseph's immediate reaction not to reveal himself to his brothers was quite understandable.  But the events that followed were rather unusual.   If Joseph just wanted to hide his identity from them, he could have ignored them.   He did not have to entertain every foreigner who came to purchase food.  So why did he accuse his brothers of being spies?  Why did he return their money?  Later, when they came back, why did he plant his special cup in Benjamin's bag?  Was Joseph just 'teasing' his brothers (to get back at them) or did he have a strategy, some sort of 'master plan'?  

First, Joseph wanted to determine what happened to his younger brother Benjamin, since Benjamin wasn't with the brothers the first time they came to Egypt.  Maybe Rachel's sons had been rejected, he thought. Therefore, his primary goal was to find out if Benjamin was still alive.  If he was, then Joseph could question Benjamin concerning what 'really' happened in the family, and afterward he could re-unite with his family. If Benjamin was not alive or if his father was already dead, then Joseph may prefer not to reveal himself to his brothers. The 'spy accusation' allowed Joseph to question them concerning their family without raising suspicion that he may be their brother.

Even when Benjamin came, Joseph still did not question him.  Instead, he returned their money and planted his cup in Benjamin's bag, in an attempt to create a situation that would prompt his brothers to repent.  

"Alas we are guilty, for we heard his crying out (when he was thrown in the pit) but we did not listen ... therefore this fate has befallen us..."  (Gen 42:21-23) 

Even though Joseph may have forgotten his dreams for some twenty years, when his brothers arrived in Egypt and bowed down to him, it suddenly dawned on him that his childhood dreams were actually coming to pass after all.  If Benjamin was still part of the family, as his brothers claimed, then he was still part of the 'selection' process.  Suddenly,everything was falling in place.  Joseph knew that his family must ultimately unite, under his leadership (as his dreams suggested).  At that point Joseph was ready to reveal his identity to his brothers but would they be ready to face him?  The shame of their relationship with him could create a barrier between them...  Therefore Joseph determined to reunite the family, restrain his emotions for a few more weeks, in order to create a  true family unity, both physically and spiritually.  He indeed was becoming a true leader!

The test that Joseph created for his brothers to redeem themselves, required them to forfeit their lives in order to save Benjamin and make them wonder and think.  By planting his cup in Benjamin's bag, not only would Joseph find out whether the brothers had truly repented, but the brothers now had an opportunity to prove to themselves that they have changed - that they are indeed men of virtue!  Only after they demonstrated willingness to give up their lives for Benjamin they could face Joseph as a brother, and unite once again as a complete family.

By the end of this entire episode, YHVH created a situation that would guarantee the physical survival of the nation of Israel during the famine and also set the stage for their exodus out of Egypt, while Joseph brought unity between the families.
Throughout the generations YHVH was watching over Israel's history, making sure that they survived, by creating opportunities for redemption.  As we enjoy His providence, it remains our own responsibility to make sure that we remain united as our destiny unfolds.