Family history isn't the whole story
Your family health history holds valuable information. But it doesn't provide all the information you need.
Some health conditions are easier to trace: Because of the complex ways that many condition-related markers are inherited, your family history may not reveal all the important DNA traits you carry. Some health conditions are easier to trace through a family. If many people in your family develop a particular form of cancer, for example, you are more likely to be at increased risk yourself.
Other health conditions are hard to recognize: But many health conditions surface less often, making risks harder to recognize. If someone in your mother's family developed lupus two generations ago, and someone in your father's family also developed the autoimmune disorder three generations back, you may have inherited an increased risk yourself. But this risk would be harder to detect by looking at the health of your immediate family.
For many of us, family history also holds more questions than answers. Some family health conditions may not have been discussed or recognized as a shared concern. Your mother's family may have a few members with diabetes, but no one might have realized some of their risk was genetic. Family health knowledge often has gaps, or can be vague or even incorrect. You might know your grandfather died of heart trouble, for example, but not know the specifics of his condition that could inform your own health risks.
To understand your genetic predispositions, you need to look beyond family history and turn to genetic testing to learn about your own DNA.