My mother died in a car accident not long ago. Some people say that one of our ancestral graves is empty?

It means that your sister's boss can infer these things with divination. Another angle is that your mother's ancestral grave is really bad, which is not good for men. Your uncle and your father represent the family and the Feng Shui family respectively. This is a problem. Find a feng shui master to take care of the relevant graves. So is your house. Change it if you can. If not, you can find a way to buy a new one.