Yes I remember that, BUT could it have been a lie that Farraday told to hold over Bobby's head that Bobby found out about and went with to keep JR from Christopher?
What? How does that make sense? Farraday told Bobby that Christopher was J.R.'s son when he initially contacted him about arranging a deal to hand him over. He fully expected Bobby to then give Christopher to J.R. and that would be the end of it. He had no reason to expect that Bobby would try to hide that and adopt Christopher himself.
That's why I'm wondering, IF it's possible Christopher could still be JR's son (obviously anything is possible on a soup as we've seen, lots of inconvenient story lines can be ignored but I mean without ignoring anything, is it possible that deception occurred).
Logically, at this point no it's not possible. As you say, of course it's a soap opera so theoretically
anything's possible. But the time to do that story would have been during the original series, while Larry Hagman was still alive to play J.R., to see him and Bobby deal with the revelation. By the time we got to DallasTNT that time had passed, especially now that Larry's dead and so is the show.
But I'm sure you could explore this in your fan fiction, if you want.