Rashi in Yaakov’s Mussar to Shimon and Levi (Vayichi 49:5) says that it could have only been Shimon and Levi who said let’s kill Yosef when he came to meet them in Doisan. We see that Reuven and Yehuda did not want to kill him. It could not have been the Bnei HaShfachos since they got along with him, and it could not have been Yisachar and Zevulun who would not have spoken up in front of their older brothers. That leaves Shimon and Levi.All the Meforshim ask why did Rashi need a separate reason for the Bnei HaShfachos. Why did he not say that they too would not speak up before their older brothers? The Shalal Rav brings from Rav Yehonoson Eibshitz that the reason a person must respect his older brother is because he did not damage his mother’s womb on the way out. A younger sibling owes their entire existence to the peaceful exit of the older ones. This would only apply to brothers from the mother, but not from the father. Therefore the Bnei Hashfachos would have no problem speaking up before Shimon and Levi and Rashi must give another reason.
The Shvus Yaakov says that there is an additional din of respecting your older brother. That is that the oldest son is his father’s right hand man and therefore out of respect for your father you must respect him. According to this reason, you would respect only your oldest brother from your father. According to Rav Yehonoson Eibshitz you must respect any older sibling from your mother, possibly even your older sister.