Shabbos Dec 25 1993 heard at Ohev Shalom in NYC

Yosef was trying to cause his brothers difficulty to atone for their sins to him. The Torah says that "Yosef could not bear anymore all that was upon him" (commentaries say he couldn't continue the cleansing of his brothers from the sins that they did). So he revealed who he was. Yosef wanted to entirely eradicate theirs and future generations of the sin. But we see later the Jewish people suffered for the selling of Yosef.... had he held out longer it would have atoned for even more future generations.

When his brothers didn't know who he was, Yosef asked about the welfare of his brothers' old father. From Yehudah's answer it is indicated that the father was still alive. Then when Yosef revealed himself he again asked "od avinu chai" (Is father still alive)? The Kli Yakar explains that Yosef thought maybe Yehudah had said Jacob was still alive dishonestly just to arouse mercy that there was an old man who would suffer if Benyamin wasn't returned.