Do you even know your medical history? Could you write it down and give it to your doctor? I know the doctors always ask if you have had or if there is any family history of about twenty different things at one point or another when you first start seeing them. But then do they ever ask again? No.
But you should tell them about significant health issues periodically. It is recommended this is done every five years.
I am impatient. I tell my doctors more often. Every time I have aches and joint pain, I tell them how my mother has rheumatoid. Every time we talk about my bones and osteopenia, I tell them about the osteoporosis my mother, aunts, and grandmother had.
If there is no medical history of a diagnosis in your family, it doesn't mean you can't get it. But if there is a medical history of something, you may be more likely to get it.
Actually, I think anytime a family member member is diagnosed with anything more than the common cold, you should mention it to your doctor on your next visit. It adds to the big picture of how you are doing. If a family member is diagnosed with a significant something... like that little thing called cancer... it adds a huge amount of stress on you. So speak up and tell your doctor. Stress is a nasty thing that can cause you to grind your teeth, prevent sleeping, and cause depression and other issues.
In the meantime, go home, sit down and write your family medical history down. Then go back and update it as needed over the years. Give a copy to family members as well.