Captured By the Alien Prince by Celia Kyle

Alien warrior, Grux Lorrz, thought his brother was an idiot for the whole “pro-bono case” thing, but all of a sudden, business is picking up. With his brother disowned by their father—the king—and off making plans for a life with his human mate, Grux finds himself taking charge of their private investigation firm. (Though he doesn’t like the administration work that comes along with it—that was always his brother’s thing.) With jobs rolling in from all over the galaxy, the brothers are forced to split up, and Grux ends up on the planet Xoyosis, a dark hovel of a place notorious for black market auctions and dirty deeds. A wealthy Xoyosan family has lost their prized house slave, and they’ll pay good money to get her back.
Human Scarlett Mason was born on Earth but kidnapped from her parents at an early age and was sold to the highest bidder at a Xoyosan auction. She’s spent the last twenty years being used and abused by the family who purchased her. She bided her time until the right moment and escaped… Now, she has no idea what’s in store when Grux gets on the case. There’s nothing he can’t find.