My sons attend private universities. Sibling #1's university requires every student receiving need based aid, who says a sibling is in college, to submit verification of enrollment from the sibling's university. There is a form that is filled out by the financial aid office at sibling #2's university, and returned to financial aid office at sibling #1's university. This is done every year. Sibling #2's university has a similiar form, but they do not require it of every student receiving need-based aid, just selected ones. Both say clearly that financial aid awards will change if the sibling is not enrolled, and you could have to pay back money you were awarded in first semester/quarter. These are both universities that meet 100% or nearly 100% of need. I don't know if other universities are as strict.