Diane Keaton has revealed that she is currently working on a book about her younger brother, Randy Hall, who has been struggling with dementia.

“I’ve spent a lot of time in senior living facilities [recently] with my brother, Randy, who has dementia,” the 73-year-old actress told PEOPLE.

“I’m writing a book about him. He always had mental issues. Nobody could figure it out, really.”

She said Hall, who was diagnosed with Parkinson’s disease before developing dementia, is unable to walk or talk now. 

“I don’t know if he knows who I am.”

Keaton explained that her 71-year-old brother “has had a hard life … He’s a very interesting person. Very sensitive, a writer and poet. But also a big drinker, and completely solitary. It’s so complicated.”

Despite her sadness over his condition, Keaton said she is impressed by the support he receives at the senior living facility where he resides.

She is also amazed by the people she met at the ward, where she visits him every Sunday. 

“There are fabulous characters on the dementia ward,” she said. “When you’re there with all of them, it’s not like, ‘They’re really weird.’ They’re people.”

Since the death of their parents, Keaton has taken over the role of supporting her brother. Keaton and Hall also have two younger sisters, Robin and Dorrie.