This marriage will make him a full-fledged king and save the kingdom from war, but is it true that he hated everyone so much and was a cold prince

the boy lived peacefully in his family, but a tragedy occurred in the royal family, Queen Ai died.  her son, who was bright and cheerful, became withdrawn and cold.  He and his sister now had to watch over everything.  But Aqua took everything upon himself.  He was alone because of this he became cold and hated everyone except his sister.