I posted this on the Internet Movie Database message board for BBM. So I don't have to retype it ... here you go.

After reading the story and many reviews of the movie, I devised my own theory about the sexuality of Jack and Ennis. Note: I haven't seen the movie yet, but there may be some spoilers in this. So... you were warned.
I think that both Jack and Ennis are bi-sexual however in the end they are very different sexuality wise. First of all, Ennis.
Ennis Del Mar
When we begin in 1963 I think that Ennis was more straight then bi-sexual. I doubt he would have ever considered being in a relationship with a man. Then along came Jack. Throughout the movie (or book) you can really tell that Ennis loves Jack so much but he is deeply in denile about his feelings for him. Ennis being Ennis (I could go into why he is the way he is but I would get writers cramp) I suppose. As time goes by he has trouble keeping a stable relationship with women. He divorces Alma and can't commit to Cassie. He only wants Jack but can't accept it completly. By the end of the film he seems to have come out of his *denial and understands his complete love for Jack (little late though). However, I doubt that he would ever be with another man.
My final thought: Ennis - Bi-sexual but leans more towards straight.
*DENIAL
Location: Here, there, basically anywhere
Population: You
When to visit: I hear it's good this time of year.
Jack Twist
When the movie begin, Jack seems to be definately bi-sexual. People (on the message boards) have given the impression that he had been with a man before, but at this current time, he doesn't seem to be leaning either way. Over the twenty year span (whew) that we see Jack ...... oh hell to this, I'm going for dot point.
- Marries Lureen (marriage of convienience or just married because it's the norm)?
- After 4 years meets up with Ennis.
- Constantly tries to get Ennis to live with him. Also trys to express to Ennis how much he loves him.
- Goes to Mexico ( we all know what happens there)
- Gives up on Ennis and comes onto Randall.
- Tells his parent he plan to bring a man (Randy boy) to the ranch to work with him... or something like that.
- Mystery death? (Bring on CSI)
So after all that, my final thought.
Jack - Bi-sexual but in the end he leans more towards being gay.
THERE!!