That end art!
Well, it looks like Arslan may not be the legitimate son of Andragoras after all. I'm now thinking he may not even be Tahamenay's son either. As for Hilmes, I don't think he's the current Queen's son but he may be the real son of Oroes. So Hilmes and Arslan may not even be half-brothers at all, and Arslan may not have royal blood. Whoa, this will make it even more difficult for Arslan to ascend the throne. The only way is for him to gain the loyalty of the army and people of Pars, and forever hide his heritage.
So I'm guessing that Hilmes is the son of Oroes and another woman. Then Oroes stole Tahamenay, who then got stolen by Androgoras, and her real son is hidden somewhere. This makes me wonder who Tahamenay's son and real husband is. And who Arslan's parents are. I remember they said Arslan used to live among a commoner's family. Androgoras probably chose him because he resembled Tahamenay most closely.