> If your parents are divorced or separated and don’t live together, answer the questions about the parent with whom you lived more during the past 12 months.

> If you lived the same amount of time with each divorced or separated parent, give answers about the parent who provided more financial support during the past 12 months or during the most recent 12 months that you actually received support from a parent

https://studentaid.gov/help-center/answers/article/how-to-complete-fafsa-if-parents-divorced-separated