Weird: Book of Secrets, Chapter IV [part iii]
Chapter IV, part iii: Gossip Column, New Kid, & Those Mean Hollingsworth Kids

Chapter IV, part iii: Gossip Column, New Kid, & Those Mean Hollingsworth Kids
Most were-youth undergo their first transformation as they go through puberty. However, since their father was a human, Jett and his older sister, Jade, were late bloomers. Jade had her first transformation when she was fourteen and passed away shortly after; Jett did not transform for the first time until his seventeenth birthday.