It can be either switch or a wire in between.
www.geocities.com/lmp4203/kiasport/pwrwindows2000.jpg
But..if it happened at same time for both rear windows and they would not work neither from front or rear switch, that is rather puzzling.....the only possibility to explain that being a cut on the ground link within the main switch between 2nd and 3rd switch on diagram....
....will the right side window work from the right side door switch ?
...if it was a problem with the KILL switch, they would still work from the main switch..and the right front would not work from the door either.
...I would open a door and check for motor operation with direct 12V and ground feeds....