Forgive me if I am repeating myself here.
In the book, when Ennis is talking about his brother and sister and he is with Jack up on Brokeback Mountain, he says his sister was married and lived in Casper. But, he only said that his brother was in Signal.
I am a middle son. My older brother, Lewis, was more like an Ennis in a way in that he did get married after he was 23 years old.
Lewis married the only gal that he had ever dated and he was already 23 when he met her when he was going to automotive school in another state (the rest of the family was in Oklahoma). It would be too off-topic to go into detail in regard to what my late mother thought about how he got hooked up with her in the first place.
Up until that time, it seemed that Lewis took every opportunity possible when it came to sexual contact with guys. We have a cousin, Edwin, who is the elder son of Dad's brother who was 6 months older than Lewis. When we would go out to the uncle's, Edwin and Lewis very often would take off to a place on the property where the folks could not see them so that they could get their hands on each other. After Lewis was 18 years old, he lived at the uncle's a number of times and he slept in the very same bed as Edwin. My older brother passed away in Sept. '88 a few days after his 48th birthday. He was born with heart problems.
Unlike my brother, I dated girls and women when I was in the closet; and did so until after I was 35 years old.
When I was teaching in a suburb of Joplin, MO, there was an identical set of twins which were in the high school and attended the same independent Pentecostal church that I did. While they were identical in looks, one was more interested in sports and the other in music. But, both of the were equally talented when it came to singing. Both of them went to college and after they were graduated, one became a high school PE teacher/coach and the other became a piano teacher, giving private lessons.
The artistic literary license taken by the screenplay writers and by Ang Lee sometimes gets completely away from various parts of Annie Proulx's original story.