Are these questions, "Is either of your parents a physician?" or are they like, "Did either of your parents earn their medical degree or do their residency at our school?" The first question would make sense if they thought you might have a good understanding of medicine if your family was involved in it, while the second one seems to support the legacy theory - that they will give you brownie points if your parents are alumni, and also that they think that you're more likely to choose their school if that is the case.
I don't think the parents' occupation factors in much into the admissions process - it could help you because of the above reasons, but it could also hurt you if they thought you were more likely to become a specialist because you were a doctor's child, and they were focusing on primary care. Or if they thought, "This kid just wants to be a doctor because his daddy and granddaddy were doctors," even if you thoroughly explained your true reasons in pursuing medicine.