Everyone Has Parents

It's easy to think about a story's hero. The bastard who wants to rule the world. The badass who saves the day. The supporting characters. The ancillary characters. They are all important in making the events in your story happen. And they all have parents. 

It's strange to think about adults as babies. To see them crying and sleeping and pooping their diapers. But we all were. We all have an origin and they generally involve having parents that conceive and raise us. 

This may never be relevant in your stories, but think about your characters growing up. Protagonists and antagonists alike, they all had this origin. At the very least, it may give you a deeper perspective with respect to who they are and how they are more than a two-dimensional beat-the-villain-and-save-the-day hero.