The first thing Yosef asked his brothers after revealing himself is, "Ha'od avi chai?" Is my father still alive?
Everybody asks: the brothers had told Yosef during their earlier visits that their father was alive and well. Yehudah had just finished pleading with Yosef to release Binyamin because their father would not be able to bear the loss. Obviously Yaakov was still alive. What was Yosef asking?
The Igra d'Kalla explains that Yosef was not asking about Yaakov -- he was asking about himself.
Later in the parsha, when Yaakov finally was reunited with Yosef, the Torah writes that Yosef appeared to his father "va'yipol al tzavarav va'yeivk al tzavarav od," he fell on him and kissed him more (46:31). Rashi explains that it was Yosef who fell on his father's neck and cried; Yaakov at this moment was reciting shema (see Maharal in Gur Aryeh as to why.) Ramban rejects this interpretation. Firstly, it would not be derech eretz for a son to fall on his father's neck to kiss him. Secondly, the word "od" does not fit. He cried "more" -- more than what?
Ramban switches things around. It was Yaakov who fell on Yosef and kissed him. Yosef came to his father dressed as an Egyptian royal, riding a royal chariot. Yaakov was an old man whose vision was poor -- he sees this Egyptian prince approaching, showing him deference, but it makes no impression on him. Maybe he sticks out his hand for a handshake, or some such greeting. Suddenly it hits Yaakov -- this is no Egyptian prince. This is his son! He now greets his son with kisses, with tears, a greeting that is far "more" than what was originally offered.
We see from Ramban that Yosef appeared outwardly as an Egyptian. He blended into the society which he was part of for 22 long years.
This is what concerned Yosef. "Ha'od avi chai?" He asks his brothers: Is the midah of yesod (od = gematriya of yesod) which my father implanted within me still alive? Or has Egyptian society penetrated and changed me?
The gemara (Pesachim 68) says that Rav Yosef would make a special celebration for Shavuos because if not for that day he would just be like any other Joe, any other Yosef in the marketplace.
There are a lot of Yosefs wandering around in the streets. Whether by choice or willy-nilly, we have to engage with the outside world and in doing so blend in, at least somewhat.
The question we have to ask ourselves now and then is "Ha'od avi chai?" Is the spirit of forefathers still alive in us? Or have we gone too far in absorbing the culture of that outside world?
The brothers could not answer Yosef because "nivhalu mi'panav," literally meaning they were taken aback by his face. They saw underneath the Egyptian dress, underneath the royal robes, the same innocent face of their 17 year old brother of long ago who they had sold into slavery and they were astounded. So many years apart and yet indeed, the same spark of their father was alive within him.
Coming back to the Ramban's second question, the Igra d'Kalla doesn't say it, but I think maybe this is what the pasuk means when it tells us "va'yeivk al tzavarav od." Yaakov too sense that the midah of yesod, the "od" that he had implanted in Yosef, was alive and well. And so he cried -- not tears of sadness, as he had cried for 22 years, but tears of joy and happiness.