The Dream Daughter by Diane Chamberlain

When Caroline Sears receives the news that her unborn baby girl has a heart defect, she is devastated. It is 1970 and there seems to be little that can be done. But her brother-in-law, a physicist, tells her that perhaps there is. Hunter appeared in their lives just a few years before—and his appearance was as mysterious as his past. With no family, no friends, and a background shrouded in secrets, Hunter embraced the Sears family and never looked back… Read more.