Families

Everyone has them. That includes story characters.

So, what does your main character think of his family? Do they get along? Are other family members in the story? Are they alive or dead? Even if they don't show up explicitly in the story, your character's feelings towards his family will affect him greatly. And he can feel differently about different members, too: there's no need for a monolithic response to his family.

Writing prompt: write a scene with your character and one of his parents. Make sure the relationship between the parent and child is visible in the scene without coming straight out and saying what's going on. Imply.