My family's falling apart...?

Okay, I swear, my family has the most drama ever. Okay, so my mom is a theripist, and my brother has aspergers, OCD, ADHD, ADD, and acouple more disorders. My mom is a divorsed , and her wife (my stepmom) has a disorder, i forgot what its called, but it makes her think things happened that never really happened. Like one seconed were fine, and the next she thinks i said that i can do whatever i want because shes not my real mom. So today we all went garage saling and my brother (hes 15, but he acts like hes 9) started yelling at us in the car at the top of his lungs for like, 20 min because we had to go home. My step mom screamed back at him as loud as she could, and then they went into a seriosuly loud and emberrising game of "SHUT THE FUCH UP, IM MORE MATURE, GO TO HELL." soo ya. and my mom went into therapist mode and tried to tell them that there both being bad and to calm down. And my step moms brilliant response was, "SHUT THE **** UP WOMAN. GO TO HELL." And I dont blame my brother for saying, "DONT YOU DARE TALK TO MY MOTHER LIKE THAT." but it was kinda weird because, my step moms his mom too. And then my step mom called my 15 year old bro a baby when she was acting the same age he was acting. And then came more embarrising screaming. Then my step mom wanted my mom to choose between my bro and her. She said she wasnt gonna. In the end, my step mom said if he was her kid she'd the **** out of him. So now were at my dads house, and my mothers currently homeless, because she doesnt wanna be where my step mom is. I dont know if i can tke it any longer, becuuz my step mom and bro fight like, EVERY DAY about something seriously stupid, like how my bros afraid of the cats litterbox. Im only a 12 year old girl, and my familys like, falling apart. what should i do?!! thnxx (: