Mother of Jacob, Rebecca and Rachel Black. When Jacob was young she died in a car accident that was so horrible they had to nail her coffin shut. Like most adults and humans in the series, she is not important enough to get a backstory. And despite whatever influence she must have had on her children to make them into the people they became in the series, she does not warrant more than a casual mentioning. She only exists because Billy cannot reproduce asexually.
"She died in an uneventful way. I haven’t decided exactly how because there’s never been a need to set it in stone for the story (not everything is determined, despite what some think. I leave many details open until I have a reason to fix them a certain way). I only know that there wasn’t any mystery or unnecessary drama about Sarah’s death. It was, of course, a very sad thing in Billy’s, Jacob’s, Rachel’s, and Rebecca’s lives (and one reason why the twin sisters are more comfortable away from the sad memories of their home). However, Jacob was young and he is naturally resilient. He recovered well." -Stephenie Meyer on Sarah Black (Personal Correspondence #10, Twilight Lexicon) Yeah of course, thats all probably because children don't need to have a mother. Its the mother who needs the children! Need evidence? Look at Renesmee. Thats why Jacob didn't really feel the need or felt sad at the death of his mother... even if he was a child, when growing up you need TWO PARENTS. Its difficult for children to grow up with only one parent and of course its difficult for the parent too. And now look at her very intelligent answer: "Not everything is determined". Of course you dont expect an author to have thought about the livestory of every minor character but there should be at least a sketch if that character is mentioned in the story. At least she should have thought about the relationship of her and Billy, because he is not dead and has a role in the story. Besides she is the mother of a character that plays a very important role. She could have thought about the influence of her death on Jacob - but oh, sorry it didnt have an effect on him because he is resilient! And to give an example of a good author: J K Rowling sketched EVERYTHING in the world she created. When the film makers asked her about a minor detail she faxed it in Minutes time. She had the whole Weasley and Black family tree sketched. She knew about the lifestory of every person in the age of Harry who appears in the story. You can ask her away anything and she answers without hesitation - she knows everything about her world. Another example? Look up J. R. R. Tolkien!