Surviving as the Sickly Younger Brother of a Villain

I reincarnated—was it possession? transmigration?—into a 19+ dark romance fantasy novel. As Serjin Dellensing, the first victim in the original story. He was betrayed by someone he thought was family, had his mother, name, and entire life stolen, and died a miserable death when his chronic illness worsened. His body is frail, his education lacking, and in a noble society dominated by Alphas, surviving as a Beta is nearly impossible. The only thing he has going for him? A heartbreakingly beautiful face. I couldn’t care less about the original plot. What mattered was saving the mother—who, in the novel, is executed by Serjin’s older brother. I had to appease that psycho just enough while finding a strong marriage prospect or an ally. Before they discovered I wasn’t a true Dellensing and stripped me of my surname—or worse, exiled me. But then… “You said it yourself before, didn’t you? That your body doesn’t react to pheromones, and that I should come find you if I ever needed someone.” “I’m just glad… you’re my little brother.” “Only you could do this. You’re the only one I can show this weak side to… because you’re my little brother.” Turns out he’s not just a psycho—he’s a twisted pe*vert who lusts after his “little brother.”