There was little known of Farhad among the foreign nations. To them, he was just a cynark asset, as for his talents, barely anyone truly understood. And if not for the involvement of the Radiant Order as well as the Church of Red Sun, even the little information they had at hand wouldn't be as detailed.
Not to mention, barely anyone knew that the monster that had terrorized the borders with Langurt was him. So Arbood didn't put the two and two together, nor was he aware of what kind of bloodline Farhad carried.
However if there was one thing that made him much more aware of Farhad's identity, then it would be Farhad's father.
"You will be correct, I am his son," Rosso spoke without shame or fear. After reaching a certain level of strength, there is never a need to hide behind masks anymore. For strength reigns supreme and the ones in front of him barely seemed strong. Including the only dwarf without armor Gael.