Robert Duncan was born in Oakland, California. His mother died at his birth and his father was unable to raise him. In 1920 Joseph and Minnehaha Symmes adopted him. Only after his discharge from the army did he take the name Robert Duncan, a composite from his birth name (Edward Howard Duncan) and his adopted name (Robert Edward Symmes). He attended the University of California, Berkeley but never finished. Duncan explored the topic of his own homosexuality and homosexuality in society in his writing.