Do I have a right to be mad?

Okay well, here is a little background information. I am 15, and I have an 18 year old brother. 3 years ago, my mom moved out of our house, leaving my dad. But they never got divorced, there "separated". They still go out together and act mostly civil. P.S. My mom moved out because my dad is an alcoholic. Me and my brother both proudly live straight-edge lifestyles, and are repulsed by alcohol. Tonight, my mom and dad went out, and they both came home drunk. As if having one idiotic parent werent enough. So drunkenly, my parents said that they were going to my mom's apartment to "let me sleep" a.k.a. have . And its terrible because my mom just uses my dad for money. So, as usual, the house belongs to me and my brother tonight. Neither of my parents are ever home, and it sucks. I feel like crying. Does anyone have any advice for me? Do I have a right to be mad?