Diane Keaton has a new book out. It’s called Brother And Sister, and it is a memoir about her relationship with her brother. Her brother suffered from mental health issues and addiction. And Keaton reveals that Randy inspired a character in Annie Hall.

Keaton starred in Woody Allen’s Annie Hall (1977), playing the title character. Allen drew a lot of Annie’s character from Keaton (including Keaton’s real last name – Hall). In her new book, she reveals that her brother, Randy Hall, inspired Annie Hall’s brother, Duane.

Duane was played by Christoper Walken, and had a memorable scene where he is left alone with Alvy (Woody Allen), making disturbing comments. He later makes everyone uncomfortable on a drive. There were more scenes with Duane that were cut from the finished film.

It seems that Keaton’s real life brother Randy had suffered from mental health issues for most of his life. Keaton told PEOPLE:

“Reality, you know? Reality was not something Randy could handle.”

Here’s Keaton talking about the book on ABC’s Good Morning America:

The two siblings grew apart when Keaton found fame. Her brother is still alive, and Keaton’s relationship with him has grown closer over the years, as he deals with dementia.

This is the third memoir written by Keaton, followed by Then Again (2011) and Let’s Just Say It Wasn’t Pretty (2015). The latter of the two is the most traditional memoirs and covers a fair bit of her early film career with Allen.

Brother And Sister, and all of Diane Keaton’s books, are out now.