Now, I don't know if this is a bug per se, or more of a you-interrupted-the-dialog-string-somehow-issue (to be honest, I know more about goblin mating practices than I do about modding

I did find a fix of sorts for Yoshimo, which involved loading an earlier file from before I gave him the boot. By keeping him in the party at all times, things managed to work out chatwise. I guess the same might work for Keldorn (i.e. no resolution of family issues).
I guess if I ever start a new file, the easiest thing to do is have Keldorn and Yoshi in party before reaching Kova. I think I'll wait until the ToB section of the mod is out first, though (yes, I know, nutty completionist that I am)