Adric’s Heart by Rebecca Rivard

She’s the one woman he can never have…

Cougar shifter Adric Savonett is the youngest alpha in the world-and not because he’s a nice guy. He and his sister are alive today thanks to the ruthlessness he hides beneath his cocky rock-star exterior. But now his sister is in danger from a dark fae prince.
Dolphin shifter Rosana do Rio might be young and inexperienced, but her heart recognizes Adric as her mate. Unfortunately, their clans are bitter rivals, and Adric is damned if he’ll play Romeo to her Juliet.

Then Rosana comes to him with an offer he never expected. That one night he’s craved with her? She’s ready.
He shouldn’t say yes, but he can’t resist.
But that one night sets off a deadly chain of events, and the two find themselves locked in a battle with the malevolent fae prince-with Rosana as the prize. Adric must choose between saving her…or his sister.