We all have personal issues – trouble with co-workers, family difficulties, unfulfilled hopes or dreams or a moral dilemma.
Though it is not necessary, every character can benefit from having a personal issue with which it must grapple or a belief system that comes under attack.
A moral dilemma, worldview or philosophy of life helps your characters come off as real people, rather than just functional players in the story. In addition, readers identify more easily with characters that have an internal struggle, and care about them more as well.
Consider each of your potential cast members, one by one. Read their entire dossier so far consisting of their list of attributes, self-description and perspective on your story.
If a belief system, personal code of behavior, philosophy, worldview, moral outlook or internal conflict is indicated, note it and write a few words about it in their dossier. If a character has emotional issues regarding themselves, their world or the people in it, note that as well.
If you don’t see such an issue already present, read between the lies to see if one is inferred. If so, write a few words about that.
Now don’t beat your head against the wall looking for something that may not be there. If a personal issue isn’t indicated, it makes no sense to try to impose one. Some characters are better off without them.
For this step, just look over what you already know about each character and then single out and describe any personal issues it might have.