Thunder and Rain by Charles Martin

Third generation Texas Ranger Tyler Steele is the last of a dying breed - a modern day cowboy living in a world that doesn't quite understand his clear view of right and wrong and instinct to defend those who can't defend themselves.  Despite his strong moral compass, Tyler has trouble seeing his greatest weakness.  His hard outer shell, the one essential to his work, made him incapable of forging the emotional connection his wife Andie so desperately needed.

Now retired, rising their son Brodie on his own, and in risk of losing his ranch, Ty doesn't know how to rebuild from the rubble of his life.  The answer comes in the form of Samantha and her daughter, Hope.  On the run from an abusive ex who has the resources and the determination to hunt them down, thy are in danger, desperate, and alone.  Though it's no longer his job, Ty knows he can help - protecting the innocent is what he does best.  But it may cost him more than he's ready to pay to let the pair into his life.  Meanwhile, the man who ended Ty's career and almost ended his life, if up for parole and looking to finish what he started.

As his relationship with Sam and Hope unfolds, Ty realizes he must confront his weakness if he wants to protect them and, ultimately, offer the real strength they need.