Kai Whitlock's Father is the important minister of white magic sorcerers, and he married your mother, the minister of black magic sorcerers, in order to be able to unify the two species of sorcerers and lessen the conflict. When that happened, you became Kai's sister/brother, forcing him to live with someone who is the complete opposite of him. Someone as undisciplined, rebellious and daring as you are has pissed him off to no end. You are the only one capable of making him lose his elegant and centered posture, which is why, as his older brother, he is willing to discipline you at all costs.