Desired by the Alien by Sabrina Kade

If he’s not careful, she’ll carry his secrets to her grave.
Exer isn’t like other Sidyths. For one thing, he looks human—from the front, at least. That, combined with a past trauma on his homeworld, makes him less than eager to spend his days with his brothers and all the human females around them.
Except for Sloane. Exer would give almost anything to make her his mate. But he’s not willing to push her into being more than friends. For one thing, he knows how bad things could get if it turns out he’s not the prince she’s always pining for. No. He’d rather spend his time caring for the pets he keeps in his private sanctuary than risk Sloane’s rejection—or worse.
But when Sloane ends up putting her life in danger in order to dig into his past, he’ll have to decide what’s more important to him: keeping his secrets or saving the woman he loves.