When Lyxor was younger, he was avoided by everyone because of the Devour half of this inheritance. No one wanted to fall victim to the power of Devour, so they preferred not to be in the same vicinity as him.
While this broke Lyxor's heart, he slowly began to accept it. His loneliness was far too unbearable, so he decided to do other things, to pass the time.
Since his parents focused on training his twin and always occupied the training grounds, Lyxor decided to seek knowledge instead of strength.
No one asked for his whereabouts or his actions. They only made sure he was fed enough time when he wouldn't need to devour and consume people. This was also to keep him alive for the fusion ritual.
Because of this attitude, no one knew Lyxor spent most of his time in the palace library. It was there he found out about the fusion ceremony when he turned eighteen and why his family was only training his twin.
They obviously wanted him to win the fusion.