Loosely based on the song "Thank God You Introduced Me to Your Sister" by Sarah Barrios. Please note I have also posted this story on my ao3 under the user @ thatprincessgirl -- You and Sarah Miller had been roommates and best friends for your whole first year of college, so when she invites you to stay at her house for Christmas, what else would you do? You were going to have the best Christmas ever! But Sarah didn't mention anything about her sister...