No, not that series, but that was a fabulous series,  and I wish it would continue. The more I think about it,  the more I think I may have been wrong about the main character not being a vampire. 

She and her brother are not human, but I do not think they were Vampires, and work for some kind of agency. I read it sometime around 2010? I was reading a lot of Sherrilyn Kenyon, Laurel K. Hamilton, etc. I do remember the agency they worked for was not super trustworthy, and she was fighting some kind of literal darkness.

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I cannot remember the main characters name, I think her brother who also worked for the agency was named Ian but I could be completely wrong. I know this is not a lot to go on.

Paranormal book where the main charcter is female but not human, works for an agency and maybe has a brother named Ian