I have lived with my aunt for all of my high school and most of my elementary school years. She has cared for me and paid EVERYTHING for me. She also carries me as a dependent on her taxes along with my elderly grandpa. I am reviewing FAFSA application for college financial aid consideration. Can I list her as my parent even though there is no formal adoption arrangement? In my mind and heart she is my parent and has always been so.
What if I live with someone other than my parents?
It doesn’t matter if you don’t live with your parent or parents; you still must report information about them. The following people are not your parents unless they have legally adopted you: grandparents, foster parents, legal guardians, older brothers or sisters, uncles or aunts, and widowed stepparents.
If you look at other questions on that page, you'll see that there are ways to report extenuating circumstances that may help identify your particular situation, bit it seems clear that you should not list your aunt as your parent without some sort of formal adoption in place.