Soul Integrity (Book 3) by Dennis Batchelder

1980: Claudia Famosa is a Cuban revolutionary and exile living in Florida, mourning her lost husband. Xinya Xia lives in Manhattan, and has spent a lifetime perfecting her soul line formulas so she can someday find the twin brother from whom she was separated at birth. Her crooked business partner claims that Claudia can use Xinya's formulas to reunite with her husband's incarnation in her own next life, but only if she's willing to sacrifice everything and die in Benares, India in two short months.
Present: Valentina Nikolskaya, the product of this extraordinary love story, has recently given up and divorced her pre-destined husband. Her ex-boyfriend Scott Waverly claims she has been duped, and asks for her help in finding Soul Identity's missing overseers. Thus begins Val's attempt to regain her own faith, and to discover the drama behind Claudia's and Xinya's actions.
Told from the perspective of three women determined to make a difference, Soul Integrity, the third book in the Soul Identity series, is a compulsively readable and emotionally immersive adventure of faith and courage through time and history.