My Sister's Keeper is by Jodi Picoult. It was published in 2004 and later made into a movie, but I haven't seen the movie. The main premise is that a 13-yr-old girl, Anna, wants to get a medical emancipation from her parents, which means they don't get to make medical decisions for her. The reason is because Anna's sister has leukemia, and Anna was born so that she could provide her sister with bone marrow and other transfusions/transplants.
This is an absolutely amazing book written from multiple characters' perspectives. I love that Jodi Picoult's books really make you think about what's right and what's wrong, and there's always a twist at the end of her books that changes everything. This is no different. It is definitely the most emotional book I've read by her.
This is not officially a teen lit book, and it deals with a lot of different situations. I would recommend it to older readers.