Hi

Im playing BG2 without mods.

Can anyone tell me what are the incompatible party NPC´s relationships ?

I think that viconia is incompatible with keldorn, but i think that there are more.

NPCs in BG2 don't fight to the same extent they did in BG1. The only members to keep an eye on are:

Anomen: if he fails his knighthood, he may attack Aerie and/or Keldorn.

Edwin: can cause fights to break out with Minsc and Keldorn.

Keldorn: will not stand for Viconia in the party for very long. He will also attack the main character after initial Slayer transformation if the party's rep is less than 8.

Korgan: may pick a fight with Aerie.

Mazzy: will eventually attack the main character if rep falls below 5.

Haer'dalis has a problem with you if you're a male PC attempting to romance Aerie.