Gnaeus was the prince and heir of the empire, in a flashback sequence. He didn't truly want power, and was tired of the games in the court. He knew that the great noble houses were using him as a pawn, but he purposefully ignored it, because he believed that he was not meant to be a strong ruler. He was never trained to be a ruler because it was meant for his eldest brother; the burden fell upon him as his brother was slain in the Great War. Gnaeus is more like a playboy noble than a future emperor.