Well.. In BG2, there is friction between the different NPCs. The stuffy old paladin cannot stand being in the same party as the evil drow, and attacks her. You're free to help either one or let them settle it themselves (one of them dies - the drow probably since she is a weak cleric).
Likewise, Edwin and Minsc hate each other, but don't attack on sight. They talk back and forth (some really funny dialogues too) and in the end of a series of dialogues they start fighting.
Then there is the Aerie/Korgan matter. Korgan thinks Aerie is a wimpy, weak elf (which she is). Aerie thinks korgan is a meanie. After some dialogue you have to make a choice. Kick aerie or kick Korgan. Otherwise the other leaves your party.