Reuven offers to let Yaakov "kill" his two sons "et shtei bonai Tamit" (42:37) if he fails to restore Binyamin.
Let's presume that Rashi is correct regarding Yaakov's perspective. Rashi (42:38) explains that Yaakov saw Reuven's offer as though it were offered by a "B'chor Shoteh." How would Yaakov gain through killing his own grandchildren?
What different perspective did Reuven have? Why did Reuven offer to let Yaakov kill two sons, and not one or four? Come to think of it, just what was Reuven thinking?
My friend, R' Joel Stern, explains Reuven's POV. After Yehudah sells Yosef, he later buries his first two sons back in Parshat Vayeishev. Reuven didn't know why those two sons died. He assumed that it was G-d's punishment to Yehudah for "selling Yosef." Now we know why Reuven offered to risk two of his children.
Reuven offered to risk his sons based upon his perception of the deaths of Yehudah's sons. However, Yaakov was, after all, clueless about the selling of Yoseph. He couldn't have seen the connection to Yehudah. Yaakov thought Reuven's offer was "shtuyot" because it was pointless to harm his own grandchildren.
Interestingly, it seems that Reuven, like Yaakov, misunderstood related situations. Like Father Like Son?