Responses
(Spoiler) You are right about everything and yes the duke has been abused! Though as time goes by both him and the duke will start catching feelings for each other. Honestly both have suffered in different ways...
beta
Ok, so Dev's goal is to find his mother and sister. And he is willing to do anything to do it. Plan A (seducing the Duke) failed.
Maybe asking for help could work...? Or not. The Duke doesn't seem to care much about the world around him. Not that Dev would ever ask. He doesn't trust the Pel (rightfully so) and his family is his weakness. They could easily be used against him. Let's see what plan B will be.
Btw, I'm still under the impression that the Duke has been abused somehow. The people around him are super creepy and the way he acts makes me think he is trying to escape reality by ignoring it.