1)
What is the meaning of "Shimon Achi"?
1.
Rashi #1: It is Shevet Shimon; they will help Yehudah to conquer his portion (Malbim - because Shimon inherited amidst Yehudah - Yehoshua 19:1).
2.
Rashi #2, from Temurah 16a: Osni'el is Yabetz 1 . His real name was Yehudah, brother of Shimon.
1
Yabetz is mentioned in Divrei ha'Yamim 1 4:9,10, shortly before Osni'el and Kalev. (PF) Maharsha (16a) - he is called Osni'el because Ano Kel (Hashem answered him). He is called Yabetz, because he Ya'atz v'Rivetz (counseled and spread) Torah.
2)
Why did Yehudah say "Ale", and Shimon said "v'Halachti"?
1.
Malbim: Yehudah needed to conquer in the mountain, and Shimon in the plain.
