'You were a good boy' ... Growing up, Chicago brothers discover their father's friends all were mobsters. They wrote a book.

Childhood is, or should be, a time of innocence, and for a while that is the way it was for brothers Michael Jr. and Jeffrey Gentile. And then a pistol fell out of a coat. "We were taking the coats from people who had come over to visit our parents and this gun just dropped on the floor," says...