For FAFSA, you will put your mom and her spouse on your FAFSA form, plus any spousal or child support you receive from your other parent.
The parent you live with the majority of the time for the year prior to the date you file your FAFSA is the parent (and spouse) that you use.
If you end up applying to schools that use the CSS Profile, your mom will complete the Profile, and your other parent will complete the non-custodial parent Profile if required.