Just wondering is it possible to have two impact characters.Answer:
Generally, you have a main character and an impact character who represent opposing approaches. At the climax, the main character must choose whether to stick to his approach or switch to the impact character's.
However, in some stories there is a main character who has no conviction, no established approach. The difficulty is that such a character has no reason to disagree with the impact character, and therefore no inner conflict. So, to make sure there is some inner conflict, the writer may provide two impact characters who represent different approaches. The main character must then decide, at the climax, whose approach to adopt.
There are also novels with more than one main character (and therefore multiple stories that are related). If all the stories are fully developed, each main character will be paired with his/her own impact character.
For example, in some romances, both the romantic leads have their own inner conflict, and each can be the impact character to the other.