The aunt has now made threatening phone calls to the uncle that if we don't go to the location she chose, her daughter is not going. And how could we make her spend Thanksgiving away from her daughter (dude what about your son who was not planning on going?)? There has also been "she/he's not even a [insert last name here]! Why should we even include her/him?" bandied about.
And now the uncle is sending me emails essentially detailing his relationship with his sister. Curse my "tell me everything about your life" face!