I'd imagine something is going on. I can understand that some bonds are so strong that we just can't stay apart for more than a year. Love can be like that, I don't think it's very common but I believe it can be like that. So awww.
Unfortunately I don't think this is that situation. I think there's some sort of sexual or financial or both type of thing going on. I don't think Chris is someone who "loves" or would know how to love a person deeply. If Chris did find his true heart sweet well damn, maybe there is someone out there for everyone.
From what we know of Chris' past relationships (both romantic and otherwise), his version of love generally requires there to be a component of being served by the relationship in some way. Whether that's getting a bunch of Legos or the possibility of china doesn't really matter: he's largely in it for himself. What the other person wants or needs is always secondary, and his narcissism and entitlement are predominant.
Given the parents that both Bob and Barb were, this isn't too surprising. Neither one of them seemed to be staying in their marriage for any reason other than that they'd had a tardspawn, and neither one really seemed to care too much about the other. On some level, sure, there was attachment there, but I'm not convinced that it was a relationship that wouldn't've fucked up even a mentally-developed kid who had to watch it growing up. It was a shitshow, and a huge contributing factor to Chris' later failures in life.
For anyone who may be wondering, that last sentence doesn't mean that I have sympathy for Chris. Pity, yes, but he has dug his own grave so many times over when he knows better that there's a reason why Kick the Autistic is America's #1 game show.
But I'm looking on the less lovey-dovey side and more on the flutter is getting some kind of benefit from this that isn't the soulmate search fulfilled.
She was a prison penpal, which makes her predisposed to develop a relationship with the inmate(s) she's writing to. Sure, that doesn't happen in every case, but it's pretty common. Best guess: their correspondence started what turned into a long-distance relationship while Chris was in prison, she came to visit shortly after he got out, and things continued from there. On the surface, it makes sense.
There is a large degree of 'follow the money' that needs to be looked at, however. It's doubtful that either one of them has the financial resources to pull off the amount of travel being undertaken, so someone is likely at the very least partially - if not completely - bankrolling the relationship. If this is the case, the obvious suspects might not be the ones in a position to do so. Until more details come into view, though, it's all speculation.