Long Shadows (Common Law #1) by Kate Sherwood

LA cop Jericho Crewe got the hell out of Mosely, Montana, when he was seventeen. Fifteen years later, he’s back, and everything is just as messed up as when he left. He planned a quick visit to deal with his injured father, but of course things are never that simple. Family complications, police complications, social complications—and, as always, Wade Granger complications.
Jericho and Wade had been so close, once upon a time. First friends, then more than friends—and then, after Jericho’s escape, nothing. Wade’s magnetism hasn’t been lessened by a decade and a half apart; even when Jericho learns that Wade is the prime suspect in the death of Jericho’s father, the old connection still sparks.
When Jericho’s newly discovered half siblings are kidnapped, he needs to trust someone to help him find them. Wade’s a terrible choice, but Jericho’s never been known for his good judgment. Anyway, he’d rather make a bad decision with Wade than a good one with anybody else.

A cop who comes back to the town he escaped when he was a teenager. A friend/ex-lover who never left but blurs the lines of right and wrong on a regular basis. Oh, this series is going to be fun.