Grave Secret by Charlaine Harris

Harper Connelly has a special gift. Ever since she was struck by lightning as a teenager she's been able to find dead people. On this trip back to Texas to see their sisters, Harper and Tolliver are pushed back into the past when they learn that Tolliver's father has been released from prison and he's seeking forgiveness now that he's clean and sober.

Harper and Tolliver, who are not related by blood but grew up together, are finding it a challenge to be seen as a couple now and the only people happy for them are their little sisters who just want to be be able to wear long dresses to a wedding.
But in the process of getting reaquainted with their family some disturbing realizations come to light about the long ago abduction, and probable murder, of Harper's older sister Cameron. During Tolliver's recuperation from a gun shot wound they drive back to the scene of Cameron's abduction, see the scene with eyes of adults and learn that their current case and the lives of their family are most assuredly interwined.