Why did Reuven insert the word "v'Gam"?
Rashi: To include the blood of Yaakov. 1
Ramban #1: 'I previously told you not to harm Yosef, whose sins were due to his youth. 2 Now the cruelty (that they themselves mentioned in the previous Pasuk) is being sought and is causing our affliction.
Ramban #2: Even though they did not actually kill Yosef, his blood was being sought as if they had.
Seforno: Our blood is being sought not only due to our cruelty, as you thought, but also because we planned to kill him as if he intended to kill them, when in reality, he acted out of childishness, without intent.
Whose suffering was akin to death.
Since he was sold as a slave, in all likelihood he had died, bearing in mind that, due to his status as their father's favorite son, he was unaccustomed to working. The Seforno too, writes that he had definitely died (due to the hard work and conditions). This was why he pleaded with his brothers not to harm Yosef.
What was Reuven's rebuke? He suggested throwing Yosef in a pit [to die]. Even though he intended to return him to Yaakov, he had not told them! They only sold him!
Ohr ha'Chayim: My main point was that we have Bechirah, which can harm even a Tzadik, so "v'Yad Al Tishlechu Vo" (37:22). Likewise, you should not have sold him to people with Bechirah! Had you left him in the pit, he would die only if he deserved to die! You are liable for the sale itself, and not only for not having mercy when he cried!
Malbim: You are liable for the sale itself, and not only for not having mercy when he cried! There were three reasons for this. (a) He was only a Yeled - he merely acted like a child. (b) I warned you, and you did not want to listen. (c) Even if you held that he is liable, he was not Chayav Misah. Slavery is like death.
Ha'amek Davar: Shimon and Levi said that primarily they are guilty (refer to 42:21:1.1:1). We are all equally guilty! Yosef did not speak amidst an evil heart, rather, mere childishness. We are liable not only for the sale. Perhaps he died amidst afflictions, and he was not Chayav Misah, and we are liable for this! They accepted Reuven's words, and each brother blamed himself.