I've been trying to sort out my thoughts about how Ennis' and Jack's experiences of being raised affected their views about, and abilities to parent. Ennis and Jack both had utterly appalling experiences inflicted on them by their fathers. They both, in sharp contrast, were gentle with their own children.
When Ennis was orphaned, his brother and sister "did the best they could", but once he was 19, "no more room for" him. He wasn't a child any more, but he was certainly an inadequately parented young adult.
Jack's folks didn't "run him off" (at least not permanently) since he went back Lightning Flat after that first summer, but home for him, from what we see, seems to be, at best, more about obligation than love and joy. He seems to take joy in Bobby in the early years of his childhood, but the despair that grips Jack as Ennis keeps refusing a life together, seems to sap that joy also.
The anger at their lives that both Jack and Ennis feel spills out, and their children witness it, but it's never directed at the children. That alone isn't enough to make them 'good' parents, not by today's standards, but it's certainly more than they were given by their fathers.
And Jack and Ennis gave their kids a lot more than that.
Again, maybe not enough to make them good parents by our lights, but they were parenting 40 years ago, and doing a much better job than their fathers. Is that enough to ask, that each generation will do better than the one before?