CSS Profile (which Brown requires) will also require the financials (incomes, certain assets) of your dad’s new spouse, in addition to that of your two parents.
Run Brown’s net price calculator with the income and assets of all three adults, as well as yourself, to get an estimated cost of attendance. It would not surprise me if you are determined to not have any financial need. Do the collegeboard npc here: https://npc.collegeboard.org/app/brown
Have your parents given you an annual college budget? If not, that is where you should start.