I'm pretty sure you can only put one state as your state of residency. Which state do you file taxes in? Which state is your car registered in? That's probably your state of residency.
Other supporting evidence may be where you graduated from high school and in some states, if you are paying in-state tuition at your college (usually because of ties to the state).
Does either parent claim you as a dependent on their taxes? (not a CPA here, but I think that only one of them can do it - my understanding is that is one of the things people work out in a divorce)...