I call this the TV Show Technique of character creation. Think of a tv show, let's say Star Trek:TOS. When the show premiers, all we know about the characters is that James Kirk is the Captain (and looks like William Shatner), Spock is the FO (and looks like Leonard Nemoy), and so on. But by the end of the series, we know a bunch of interesting tidbits about them:
*Kirk has an older brother who was a colonist on (that planet with the flying pancake critters; I'm blanking on the name), and a nephew who survived the invasion.
*Kirk himself is a survivor of a space holocaust.
*Spock is the son of the Vulcan ambassador.
and so on.