These 2 quests both show the other quest as being the next quest in the chain. But I have done both quests on different toons and not been able to get to the other quest after getting or doing one of them
The quests in the lorebook need to have a designation to show if doing one quest locks out doing another quest as I have seen this situation in other quest entries.
My hubby and I ran into this problem over the weekend and were wondering the same thing. We both have "Northern Threat", but cannot get "Distant Relations" or "The Lost Fellowship" quests.
Yes, this is an issue with how the Lorebook is determining next quests. These quests are independent of each other but taking one prevents you from taking the other. So, they are not really 'Next Quests' of each other.
The next major release of the Lorebook should (if I've done things right... just a few more tests...) only show true 'Next Quests'; probably won't show what quest prevents another. Got to keep you coming back to play the game and figure that stuff out.