I realise there is limited time and the focus must be on the central relationship, but I do think its a shame we barely see Jack as a father. Maybe that was the point tho, we see so little of it as a reflection of how important a factor in his life it was?
I think that these lines from Annie P.'s story tell us what we need to know abouty how the boys feel about fatherhood:
“I used a want a boy for a kid,” said Ennis, undoing buttons, “but just got little girls.”
“I didn’t want none a either kind,” said Jack. “But f***-all has worked the way I wanted. Nothin never come to my hand the right way.”
That being said... Ennis adores his children, and they adore him. Alma Jr. is the one bright light in Ennis' future after Jack's death. As for Francine... who, for reasons unknown, becomes Jenny in the movie... well, we just don't know much about her.