As an author I like to create. Create worlds, cities, stories, characters, etc. Sometimes I like doing this so much I can get lost inside of it. The research that I do, for tools, inspirations, it's all great fun.
You are writing a story, in this story, you may or may not have characters in this story. Logically I would think you have characters, but I don't know what kind of bad-ass writer you are to have to skills to write a story without any characters. So in this scenario, let's say you have characters. What is the family background of those characters. Parents? Grandparents? Siblings and/or cousins?
The website I would suggest to create your fictional family tree for you amazing cast of character is called www.familyecho.com. You can signup to the site, create you family tree or trees and the best thing I like of this site you can print you family tree (Or "print it" as a PDF like I do) to keep that family tree on your computer, or your wall, what ever your heart desires.
Bones: The other thing I use this amazing family tree creator is to organize the evolutionary tree of fantasy/science-fiction races for my world building. If you find any other great tricks or have any questions about world building. Leave a comment and I will try to answer your questions with pleasure. Anyway if I don't know the answer and I do some research and get back to you on that :)