I suppose some states may have different regulations effecting the system, but every plan I've ever seen doesn't differentiate based on the number of dependents you have. Rates are effectively tiered to single, married, or family.
This varies significantly from state-to-state, by insurer, and even by plan. In places that do price based on actually composition for family plans, there's rarely a particularly linear correlation between family size and rates. (Also, good luck getting an insurer to tell you your actual rate on an online tool :/)
