The Face on the Milk Carton by Caroline B. Cooney

While they don't put faces of missing children on school milk cartons anymore, just image if you saw a picture of yourself as a young child on one. When teenage Janie does, she starts down a path to find the truth, but can she handle the truth and where it leads. She has her whole world pulled apart. Can she put herself back together? Who are her "real" parents, those who raised her or the ones she share blood ties? Does she risk her world to find out? First of a series of 4 books. EML had to face a similar problem when her birth parents found her after 42 years and found someone will get hurt everytime, it is just the way these things work out.