“Sir, you’re asking a question that doesn’t have a biological answer.”

Marcus didn’t look up from the tablet he was using to cross-reference the afternoon’s trading volume. He stood by the floor-to-ceiling windows of the library, his silhouette a sharp, dark line against the encroaching gray of a Westchester twilight.

Lucian remained in his leather wingback chair, his fingers tracing the braille-like texture of a scarred mahogany side table. The house was quiet—the kind of silence that usually preceded a storm, or a funeral.

“It isn’t about biology, Marcus. I’m not talking about cells or skin,” Lucian said, his voice dropping into a low, gravelly frequency that made the air...