Lots of people here have one or both parents in the medical profession, but then there are also lots like me who have had nobody go to university before, and definitely no doctors. As others have said, if it comes up then I would imagine it's fine to mention it, but make sure it doesn't come out as if you only want to be a doctor because someone in your family is, or someone wants you to be. It's got to be your decision based on you having enough information about medicine, and if they can see that there won't be any problems.