America's most famous cowboy won a Best Actor Oscar for his portrayal of one-eyed U.S. Marshal Reuben 'Rooster' J. Cogburn in the 1969 adaptation of Charles Portis' novel.
The Cohen Brothers have brought the tale back to life in an acclaimed new movie, starring Jeff Bridges in Wayne's Academy Award-winning role.
But the siblings admit neither of them watched the original movie before the cameras rolled.
Ethan tells Deadline.com, "It's just a very funny book... It all just seemed promising material for a movie. Which might sound funny because, as you say, there was this iconic movie. Which we were aware of but which we didn't remember very well...
"And in the course of remaking the movie, we didn't watch the first one. We weren't much worried about it, though. You say it's iconic, and that's very true. But on the other hand, I must say it's probably iconic for people our age and older. And we're not the moviegoing demographic anymore. I don't think younger people have much of a connection to John Wayne, at all. So it didn't feel like we were trespassing and we didn't worry about it. We just had this enthusiasm for the novel."