Angel of the Knight by Em Petrova

Lexi Knight has always been the sister everyone protects, and she’s never been so fed up with it. She knows her brothers are keeping something important from her, and she has news for them too—their sixth man on their special ops team Rocko has finally given in and confessed his feelings for her. If she can only find him so they can tell the family together, that is.
Matthew Rock, aka Rocko, has his life together. Or at least he did. Then he had to go and step in that mine and blow himself up, severing his arm so badly it’s not savable and ripping away his hopes and dreams of laying claim to Lexi Knight. It’s hard enough that the Knights will never see him as good enough for their little sister, but now that he’s only partially a man, there’s no way he can ask for her hand.
They say there’s no hell like a woman scorned, and Lexi is livid. Hot on the trail of the man who loved her and left her, she’s determined to make him see that she’s worth fighting her family for. And then she sees her lover’s real reason for taking off… Lexi has too much on her to bear alone, and Rocko can’t allow her to take on his issues too. Does he have enough strength left to fight back?