Wynonna has recently been named head of House Earp, the biggest house in the West. With invaders rising up and threatening peace, her regents procured an agreement with another house to secure the Earp legacy.
Royal/Medieval AU with terms taken from Game of Thrones (but not Game of Thrones AU, no dragons :)).
Hunger Games AU, where Waverly Earp is chosen as tribute for District 12, and Nicole Haught volunteers as tribute for District 2. It's the same no matter which district you're from: win the Games or die.