When your twin leaves you with abusive parents and a little brother, you have a right to be mad. And Adelicia Black was very mad at her brother. Normally, you would say that Sirius had to leave, for his own good. If you asked Adelicia, she would say that Sirius abandoned them, and left them that way. Left her parents. Left Regulus. Left her. Book 1 of The Sacred Twenty-Eight cover by @Wyllad