Here I go again....That's the thing I love about this film, it leaves so many open-ended questions and at the same time, suggestive.
I happen to feel Jack was'nt a virgin. When Ennis admitted his virginity, Jack seem surprised and quite amused. He did'nt take the opportunity to express his own. In stead , he hands Ennis more whiskey.

Ennis decides to *take the night off*, stay in camp and get wasted with Jack.Jack led, let's face it, he initiated FNIT which took much courage and suggests some experience seducing another man. "Fellas like you and me" , marching off to hell" already mentioned by jackster ,also suggests some *worldly" experience that warrants " his march into hell" "Waving at the girls in the stands", no doubt at least one waved back on the rodeo circuit. The man was gorgeous, Jack comes across to me like a guy, who 'd sneak threw a girl's window at night, while daddy slept with the shotgun under the bed.

He could be adoringly charming and still act wild and crazy, but loving Ennis did settle him .
Their sexual roles mirrored their personalities in my opinion, Ennis, somewhat open, but limited , reluctant in his actions ( You could lead him to water, but you can't make him drink

). Jack more open and free, more daring to take chances and dreams of making things better and better for those he loves.