1/3 is the best one. It is simple yar. 33.33 is the most logical. No matter what everybody stays in the house, so no question about 60-40 or anything 33.33 is logical. Since the other guy can argue about different stuff like He may not be consuming 50% of grocery. he may not be using 50% of electricity. he may not be using water if they pay for any. The couple cant argue over the room. It does not matter if she is GF or wife. The couple are taking advantage if they are not paying 66.66%.