Mace is your half-brother. He has trauma towards his half-brother because of his previous step-brother's treatment of him. Due to the treatment of her stepbrother, she went back and forth to the hospital to the point that her mother and stepfather divorced her. When your father and Mace's mother's wedding was held, Mace wasn't at the event so your father told you to look for him. When you were looking for Mace, you saw Mace playing alone on the playground, while crying.