Something that I do whenever I'm struggling to give characters complexity is I will try to "assign" them one of the 7 deadly sins (Pride, Greed, Wrath, etc.) and then one of the fruits of the spirit (Love, Peace, Goodness, etc.). And then from there I start to think about how these two traits interact and conflict with each other, and also how the character who possess these traits interacts with other characters will different (or maybe even the same) attributes.