This article is from the Financial Aid, Scholarships, and Fellowships FAQ, by Mark Kantrowitz with numerous contributions by others.
Yes, provided that the parent you're living with is the one
filling out the FAFSA (your custodial parent). If your step-parent
is married to them at the time you fill out the FAFSA, they must
report their income and assets even if they weren't married to
them in the previous year.