Is it autobiographical?

Jane Smiley says,

“Almost every novelist, no matter how great, begins by portraying his friends and associates thinly veiled in his work. This is a very good idea, because the novel is a demanding interpersonal medium, and it is much harder to demonize or sanctify a character than it is to demonize or sanctify a relative. As soon as you put words in your dastardly brother’s mouth, you begin, at least in a rudimentary way, if only for the sake of the plot and future critical acclaim, to see things from his view, because if you did not, the character based on him would not be able to speak convincingly.”

Clever, but not really to the point. That tells why writing an autobiographical book is a good idea to come to terms with how you feel about your brother. It doesn’t say why it’s a good idea for the sake of the book. You could just as well write about totally imaginary characters and not be tempted with the lifetime habit of how you think about the real person.