You can try running the net price calculator for each college for both the current situation (one in college) and for the next year situation (two in college). This should show how each school adjusts financial aid based on number of students in college. Remember that the younger one may see financial aid change after the older one graduates.
However, there could be other reasons that financial aid could change next year (e.g. the college’s financial aid budget changes, or the college assumes a greater amount of federal direct loans as the student moves up in class level).
https://ofa.colorado.edu/aidestimator/
https://www.finaid.ucsb.edu/net-price-calculator