Question about Filing FAFSA(Parents are separated)!!!

<p>Hi,
My question is, my mom and dad have been separated, not legally, for about 9 years now. My mom doesnt do income taxes because she stopped working many years ago when my brother was diagnosed with Autism. We live with my grandfather, who is retired, and my dad gives my mom money every month for me and my brother. My dad does his income tax and declares me and my brother. What do you do/need in this case?
Thank you :)</p>