ha! ha!
You say:
Look at the film and notice that LD takes possesion of the baby in the nursery scene and says that he is the spittin' image of his "grandpa", well if grandpa is the father then that is certainly true.
The whole issue of a marriage of convenience between Lureen and Jack makes more sense if LD is the father, because Jack is expendable in both LD's and Lureens eyes, it also explains some of LD's hostility. And it explains the payoff that Jack says to Ennis that LD is willing to make just to get rid of Jack. Jack is an inconvenient reminder to LD of his transgressions.
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Brokeplex, you are right that LD considers the baby an spittin' image of himself... but you do not know that he is lead to think that, possibly ?? (As both Lureen and her mother wants him to think that now !!)
But, even if indeed LD had sex with Lureen, I do not think that she is having his child, but lets her father think that, for convenience, for now in the nursery scene !!
L
Later on, he figures it out for himself that is not his love-child (is that the right expression ?), since Lureen had sex with somebody else besides Jack !!
That is why the Thanksgiving scene is finding that LD is mother-hen, and replacing Jack as father, but Jack refuses that !!
That is what I figure!! Surprised!! ??
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Waiting for your advise, (note that Jack is being abused by LD till then, and even after since he was offered $ to go away,)
hugs! And Jack does NOT go away because he was an abused child in his youth... so stays with Lureen