Quote (KitsuneYosh @ 16 Feb 2013 13:11)
The rule was that you had to kill your best friend to awaken it.
If you recall, Sasuke didn't kill Naruto either. After he had won their battle, he left without killing him, saying "I'll find my own way."
I think it can be anyone close to you. Kakashi probably awakened his because he felt responsible for Obito's death and Sasuke awakened his for feeling guilty for killing Itachi.
Also, I'm not sure why you brought up Sasuke. Sasuke meant he'd find his own way to get stronger, not his own way to awaken his mangekyo.
This post was edited by Vicc on Feb 16 2013 12:31pm