So you're saying (linear) the vehicle doesn't stop in a straight line. Does it pull to one side only? Based on your description I'd have to point the finger at either the lines or a bad caliper. You can try lines first, the less expensive route but I have a feeling you'll be replacing calipers as well.
Being that our cars sit for lengths of times not being driven funny things can happen to various systems. Also if/when you replace the components, check your rear wheel cylinders replace as/if necessary and flush the system out with good clean brake fluid, I like to use synthetic DOT 3 by Prestone. It tends to be not as hydroscopic (water absorbing) as regular brake fluid. Good for long stints of sitting around.
