SO if arduino biases the one NPN transistor, and the driver biases the other via the power window switch, terminal a and b of the motor , will short circuit. this why i am looking for a way, to make it impossible for the one relay to energize, if the other is energized. all that for one window. another 2 relays etc for the other window.
now do you understand?
In the electrical word this is accomplished by 'interlocking' the relays in questions using multipole relays (typically DPDT) where a set of contacts of one relay breaks the coil circuit of the other relay and visa versa. So on any given relay one set of contacts control supplying voltage to the load, a motor in your case, and the other set of contacts opens the coil circuit of the opposite relay, thus preventing the possibility of having to relay coils powered at the same time.