Willie Nelson and his sister Bobbie are poised to release a co-written memoir.

The 87-year-old star and Bobbie, 89, have revealed plans to release 'Me and Sister Bobbie: True Tales of the Family Band' on September 15, with the memoir set to reveal details of their relationship and musical collaborations.

A statement explained that the book will weave together Willie and Bobbie's journeys ''as they experienced them both side-by-side and apart, with powerful, emotional never-before-told recollections from their personal lives and careers''.

The memoir is being published by Random House and Ben Greenberg is serving as the executive editor of the memoir.

Willie and Bobbie have also announced plans to release a picture book in 2021, with the project having been handed a tentative title of 'Sister, Brother, Family: Our Childhood in Music'.

Last year, meanwhile, Willie announced he'd quit smoking after breathing became ''a little more difficult''.

The country music legend admitted smoking almost killed him and so he decided to change his lifestyle.

He said: ''I have abused my lungs quite a bit in the past, so breathing is a little more difficult these days and I have to be careful.

''I started smoking cedar bark, went from that to cigarettes to whatever. And that almost killed me. I don't smoke anymore - take better care of myself. I'm here, I'm glad to be here. I'm lucky to be here.''

Willie loves being able to perform for his fans and doesn't have any intention of quitting touring anytime soon.

He explained: ''I love the bus. This is my home. [Performing] is an energy exchange. They give me a lot of positive energy and I hope to give them a lot of positive energy.

''For an hour they get away from everything they don't like.''