Well first and second are purely for educational purposes, I just want to know. The third one is for the project and it is quite small.
Because i'm feeling kind of lazy i'll adress just this one. If you want to create an emotional bond between the player and this other character its good to firstly have a solid backstory about how the main character and the other character know each other. Get the other character to save the main character's life several times. Make this other character extremely optimistic and carefree, to get people feeling like he's the better half of the two characters. If you really want to impact the player get him to die while they're having a conversation about what he wants to do in the future (like his dreams and goals) in a hostile area, and then bam! he dies right infront of you. and your character has to become extremely emotionally upset about it. Or even better, as they're about to make it and they're home free he gets killed. the point being you have to get the character to be the better of the two (personality wise) you have to have a history between them, and he has to die in a happy moment to turn the mood completely around.