<p>I belive that, unless your grandparents are legally your guardians (i.e., they have gone to court and a judge has made a ruling that your mother loses her parental rights, at least temporarily, and given legal custody of you to your grandparents), the living arrangements are informal and irrelevant. You still need to use your mother’s information. It also doesn’t matter that she won’t help you; all that matters is if she is able to help you. (Otherwise, every parent would refuse to fund a college education so they could get more financial aid.)</p>
<p>And yes, the fact that your mother has claimed you a dependent on her income taxes is probably fatal to the idea of using your grandparents’ info anyway.</p>