In Honor’s Defense by Karen Witemeyer

He’s Faced Countless Perils on the Battlefield, but Nothing so Dangerous as Falling in Love.

Luke Davenport has been fighting all his life–for respect, for country, and for those unable to fight for themselves. But now that his Horsemen brothers are domesticated, he’s left alone to battle the wildness within. When an opportunity arises to take a job on his own, tracking down a group of rustlers, he jumps at the chance.
Damaris Baxter has mastered the art of invisibility. Plain and quiet, she hides in books and needlework, content to be overlooked. Until her brother dies suddenly, leaving her custody of her nephew. She moves to Texas to care for Nathaniel, determined to create the family for herself that she never thought she’d have and to give him the family he desperately needs.
When Nate finds himself knee-deep in trouble, Luke’s attempt to protect him leaves Damaris feeling indebted to the Horseman. But suspicions grow regarding the mysterious death of Damaris’s brother. And the more questions they ask, the more danger appears, threatening the family Luke may be unable to live without.