Not that I have any hope of calming Jodi or Rubystreak – I notice when two of my cats are fighting, the only thing that’ll separate them is a squrit of cold water, and none is handy over the internet – but FWIW, I think you both are being oddly intractable and blowing things out of proportion. It’s possible that you both have emnity that predates this argy-bargy, in which case, have at it.
Jodi does seem to be taking Rubystreak’s comments awfully seriously, infering the absolute worst connotation to their possible meanings. This may be a subject very close to you, in which case, I think you are wise to stop reading. I just don’t think her comments rate all the anger. Though again, if y’all have some kinda Hatfield/McCoy thing going on here at the Dope, that would explain your thinking the worst of her comments. Could well be layers here I just don’t see.
Rubystreak, I do think you are putting the worst light on the scenario by stating that the parents think it would be “a horror” or a fate worse than death for their kid to be an only child. That pretty much damns all parents who actively try to have more than one child, which I’m sure you don’t intend to do. People who love their own siblings and who want their kids to have the same peer-to-peer experience don’t necessarily think it’s horrific to be an only child. But they may think it’s maybe more fun for the kid to have a sister or brother.
I will say that in my own family’s case, there was some fairly unexamined thinking on my parents’ part as far as why they had the second course of kids after my brother died. I wouldn’t be surprised if, considering the not-very-psychologically-aware folks in my family, people around them said having a child would help my mother recover after the loss. Unfortunately I don’t know the whole story, as both my parents are gone and it was never spoken about much. (I didn’t even know of my brother’s existence until I was ten.) Mom did look on my older sister (the one born a year after the accident) as ‘a savior’, which … well, is putting a lot of pressure on a kid. And they told her that I was born to give her someone for company. Heh. Sure puts me in my place, huh? 
But they neither of them meant for this to be hurtful. They thought they were doing the right thing for all of us: for themeselves, certainly, because we reminded them of the joy that life can hold for parents; but also for my oldest sister (the survivor of the accident), who now had a pair of little sisters to play with; and obviously, for us, because we wouldn’t exist if not for this tragic circumstance and our parents’ decision to move forward and choose to believe in a future.
So for all of John/Elizabeth’s faults (obviously he has more than she does), I don’t in the least understand why anyone would question their decision to have a couple of kids. For Elizabeth in particular, she may have thought of these children as something hopeful in a life that has already been filled with far too much tragedy. And if your wife, who’s lost a child and had cancer, expresses interest in having more kids, is it really that odd for a husband not to deny her something that might make her – and him, too – very happy?