It would be funny if g-ma got pregnant. This may just be for the manga that their son is their doctor because I know it is not allowed for a doctor or surgeon to have their parents or children as their patient unless there is no other option for that needed instant, unless japan is different. Why would you want to be your parents doctor and why would you want your parent to be your doctor. Sure I have no problem seeing my parents naked, but I don't want to touch their genitals and I don't want them to see or touch mine lol