I get a lot of insight in regard to Ennis from what Annie Proulx wrote about him early in the book:
Ennis, reared by his older brother and sister after their parents drove off the only curve on Dead Horse Road leaving them twenty-four dollars in cash and a two-mortgage ranch, applied at age fourteen for a hardship license that let him make the hour-long trip from the ranch to the high school. The pickup was old, no heater, one windshield wiper and bad tires; when the transmission went there was no money to fix it. He had wanted to be a sophomore, felt the word carried a kind of distinction, but the truck broke down short of it, pitching him directly into ranch work.
. . . .
Ennis, high-arched nose and narrow face, was scruffy and a little cave-chested, balanced a small torso on long, caliper legs, possessed a muscular and supple body made for the horse and for fighting. His reflexes were uncommonly quick and he was farsighted enough to dislike reading anything except Hamley's saddle catalog.
Ennis seems to have a bit of a vision problem and that might have had an effect on his learning in school. My older brother who ended up completely his high school education by correspondence after he was 18 years old had many skills like Ennis did. I could trust him to work on any vehicle I owned while Lewis was alive. While Lewis's face did not look like the book's Ennis, he did look more like him in his build. Lewis was skinny most of his life until his illness related to heart problems caused him to gain extra weight. Lewis did have a vision problem and because he was left-handed, he as discriminated against by a teacher who thought people should only use their right hands to write.
Like Ennis, Lewis should never gotten married either. Lewis did love his children very much and the Movie Ennis loved his children, too. Lewis learned to do things by watching others do them and in contrast, it was easier for me to read a book or instruction manual to learn to do the same things.
Oh, I am amused that Ennis did not know what "Sophomore" really meant. Who would want to be classified as a "wise-fool" or a "foolishly wise person?"