The Lola Quartet by Emily St. John Mandel

Gavin Sasaki is a promising young journalist in New York City until he's fired following a series of unforgivable lapses in his work. The last thing Gavin wants to do is return to his hometown of Sebastian, Florida, but he's drifting toward bankruptcy and is in no position to sit still when his sister, Eilo, drops a bombshell. Recently, she spotted a ten-year-old child who looks remarkably like Gavin, and that ten-year-old girl has the same last name as Gavin's former girlfriend Anna. As Gavin sets off to track down Anna and her (his?) daughter, it becomes apparent that they are on the run from some very bad men.