Ben Barres had just finished giving a seminar at the prestigious Whitehead Institute for Biomedical Research 10 years ago, describing to scientists from the Massachusetts Institute of Technology, Harvard and other top institutions his discoveries about nerve cells called glia. As the applause died down, a friend later told him, one scientist turned to another and remarked what a great seminar it had been, adding, "Ben Barres's work is much better than his sister's."

There was only one problem. Prof. Barres, then as now a professor...