Dead Heat by Patricia Briggs (2015) Ace 

Anna and Charles visit Joseph, an old friend of his to get Anna a horse.  When they get there, they discover that Joseph is near the end of his life.  He’s known Charles most of his life, but always refused to be turned, in spite of the fact that his son is a werewolf too.  While there, they discover that children have been getting kidnapped when one of the family reports an attempt on one of their children.  Charles smells fay but can’t pin it down.  Such a challenge against the family can’t go unchallenged.