L is for...

Linage, as in who are their families? Ancestors? Parents? Siblings? Partners? Offspring? etc. Why is this important to know.

Even if you never use all the information that you gather on your characters linage or family, it is important to you the writer and the story you are telling. How far back can you trace their family? Whose in the family tree? Royalty? Thieves? Murderers? Daemons? Aliens? 

What's your characters parents like, did they love your character? Did they treat them well? Are they still living? How does the character think about them? Was the character abandoned by them as a child? If so, what are the adoptive parents like?

All questions that you should ask when developing your character. You don't need to go into a lot of detail here just yet, but eventually you may need to. So jot down what you know so far. 

Real live people are generally formed for good or bad by the people around them when they are growing up. This formation can led to the person either following in the peoples footprints, or deciding that they never will, that their life will change. 

In order to achieve this in your story, you should know the ancestry of your character, it's linage and its family ties and links.