Before We Were Yours by Lisa Wingate

Two stories merge into one mysterious past when the young daughter of a senator is visiting home and getting her grandmother settled at a nursing home and one of the residents calls her by a name she doesn't know and then a photo that looks remarkably like her grandmother is in the woman's room. Soon she is off to follow the mystery with the help of the son of a "people finder" and things she finds in her grandmother's things. The other story is where her people really came from.
The truth is bound to come out and when it does this "cream of the crop" family may not like that they share the blood of river boat shanty family whose children were taken and given to baby brokers.
Rich and heartfelt, this story will live in your heart for a long time and if you are like me, be amazed that places like this existed and so many families split apart forever.