I don't know, I think we should probably let it go its course and see what will come out from it, and then choose if we are going to be a single group or not(if the paladin wants to fight, then two groups, but if he eventually decides to accept the undead as an ally, then only one group).
Also, I want to point out that kidcopious didn't directly stated if the paladin recognized Harrow or not, so there might be a small chance that he didn't.