Cooney, Caroline B. Three Black Swans.
***CAUTION*** REVIEW CONTAINS SPOILERS!***
Missy's high school science class is discussing hoaxes, and she decides to bring her cousin, Claire, in to school and go on the school video announcements with the information that Claire is really her long lost twin sister. Missy thinks that people will believe it for a little while, but is surprised that everyone really does think that she and Claire look exactly alike. The video goes on You Tube and is viewed by a number of people, including the girls' parents, who become upset. The girls were both adopted, and there were irregularities in the procees that have long haunted the parents.
When a third girl, Genevieve, sees the video and realizes that the girls both look exactly like her, things get even stranger. After much hand-wringing on everyone's part, Missy and Claire decide to go meet Genevieve, who is not adopted. Here's the spoiler, so stop reading if you don't want to know-- Genevieve's mother did not want to have a baby, and when she found out she was pregnant with triplets, she hard heartedly gave two of them away. Her only concern now is that her boss will find out, think less of her, and she will lose her job. The other parents are more supportive, welcome Genevieve, and the girls find a way to stay in contact and remain sisters.
Normally, I love Cooney. While If the Witness Lied was iffy, They Never Came Back was quite good. This one... have to say I didn't like it. The tone was overly melodramatic, complete with short, choppy sentences, an overabundance of exclamation marks, and too much information about how all of the parents felt. If I didn't care, students might skip over these parts. At some points, I thought there might be some intriguing explanation about the girls, like cloning or genetic manipulation, so when it was just a mother who didn't want two extra babies, the story lost steam for me. Cooney's writing is usually smooth and facile; if you had handed this book to me without an author attached, I would have assumed it was a new writer's first novel.
Looked for reviews that were more positive, but this hasn't gotten a lot of blog attention. I'd love to hear from people who liked this more than I did.