How developed should a character be who only shows up in flashbacks and not in the main storyline? I've got this character who's got this brother. My character remembers going to a restaurant the last time he saw his brother. The story is about something else, but this character also has to take care of something for the brother. Other than that, the brother is not at all important to the story. So, how important or relevant is it to put too much into this brother? I mean, I think I've got it, but it's pretty bare bones.