Alyandra’s Shadow by JL Madore

Resistance is futile.
When Shadow wakes from a life-threatening injury he sustained defending the Defiant’s human refugees, he’s stunned at how much has changed: time has passed, his people aren’t his anymore, and his sister is building a new life with her alien lover in the underwater city of Atlantis. Seriously?
Alyandra knows better than to cross the lines of propriety with Shadow. He’s her patient, her best friend’s brother, and a Navy SEAL warrior with unnatural anger and violence brewing within. But when evil descends and survival instincts take over, propriety ceases to hold importance.