Aren is aware that he has a half-brother.
Kresi made him feel the same pain that his mother went through when she was dying. She challenged him to find her. Because of that torture, his vessels were broken. When he received the holy fire, he was in tremendous pain. It was Mayaeira Mirin, the previous Renasir and Kresi's mother, who saved him.
After he woke up, he lived like a mad man. He hunted down the cursed children and killed them mercilessly. More he killed, the worst he felt.
No matter what he did, the harbinger didn't reappear. Back then, Belan Continent was closed off. He couldn't enter Belan and find his brother. After Ari died, the Belan just disappeared. He thought that his brother also died with Belan Spirit.