can I be denied a promotions as a police officer because my brother inlaw works for the same Dept?

I am a police officer who has been working for the same agency for over eleven years. During that time, I earned by bachelors, MBA and PhD. At the same time, I have elevated myself to the most recognized police officer in the county and have been recognized on the state level several times for work related activities. Unfortunately, during the same time the police department hired a new employee who eventually met and married my sister. Now I am being denied a promotion because my brother in law works for the department. As you might guess, this has a drastic impact on my career goals. The question I have: Is the department required to make reasonable accommodations, or can they deny the promotion based solely on the fear of nepotism?