I read the summary and thought 'oh, another lost sibling' plot. Do I really want to devote 89 chapters? Yes, yes I did. You wrote in the sister with believability, redeemed Draco (you know he isn't all evil), didn't make Ron a complete arse, kept everyone within their original characters and got Severus and Hermione together (my favorite pairing). And most importantly, you finished it! You also delved into the truly evil nature of Voldemort and his followers, but wiped Severus soul. Very well written and one of my absolute favorites.