Raised by an older brother and sister after his parents' death, Ennis grew up on a ranch. He learned early to work hard and keep his mouth shut. One fated summer, Ennis found work overseeing a flock of sheep, along with Jack Twist. The two began a lifelong love affair that both broke them and made them who they were.
Ennis is a strong willed man who manages to convey so much more than words alone, often without use of words. He comes from a modern world society, and if faced with anything super natural, assuming his life wasn't in danger, he wouldn't believe it. Assuming his life was in danger, he probably still wouldn't believe it. It's hard to say how he'd react without putting him in the situation, but I would expect him to go down fighting.
Ennis would come to Chicago where his sister is in hospital, about ten yeas after that summer on Brokeback.