You were Death the Kids younger sibling. There was a difference in the way your father cared for the two of you. He had strict teachings for Kid and yet, he seemed to not mind what you did as long as in the end you'd turn out to be a shinigami

Kid stood up from his chair suddenly. He told his father he was going to join the DWMA and would leave it up for your father to enroll him. And soon, just like that, your brother left through the door. You and Death left alone..