This is where my mind goes, nothing adds up and there's so much information moving on the real relationship between these three. If Jay met Jim on a family vacation this makes me think Jay could have introduced Jim to Geraldine at some point.. but this would also mean both either have extensive conversations through either phone (seems less likely in this era due to the cost of long distance) or through letter. I know TN wouldn't be extremely far from Missouri but it's still a drive and I question how often he was going to MO or if maybe Jim did live there and this simply was missed by his sister likely due to age.. though it's so hard to verify that kind of theory.. often when you're younger you don't think as much about these things.