Jack and Ennis flirted with each other from the very first moment.
Those glances at each other were not just pure curiosity; there was pleasure in their eyes. One handsome man admiring another.
I am straight and happily married, but if I pass a beautiful woman on the street, I can’t ignore the fact she is beautiful to look at... so they did it too.
Remember Ennis sitting on the wooden steps smoking as Jack was arriving?
He turned off the cigarette... then in the bar he is asking Jack for the lighter. I’d say that’s need for contact/attention/communication/sharing.
When Jack choose the mare, Ennis was worry… you could see it in his eyes, he feared for Jack’s safety. You might say it was too soon… I don’t think so; the love was in the air already.
In the scene where Jack goes to pee not far away, while Ennis was still eating have you heard him moaning? Was it that he enjoyed the beans so much?
Jack comes back and taps on his belt buckle; he pushed his pelvis in a way that spoke of thousand words.
In all, I have to say there was no better choice than Heath and Jake to make this master piece. There was everything, from looks, chemistry, and the gift of becoming the character.