Knowing your family history can give a lot of information that helps a genetic counsellor assess:
if a condition in your family is inherited
your chance of inheriting the condition
the chance you’ll pass it on to your children
Your family history can give information about ancestry or heritage. This can be important because some conditions are more common in certain ethnic groups.
For example:
Cystic fibrosis is more common in Caucasians of Northern European heritage
Sickle cell disease  is more common in people with African, Hispanic or Middle Eastern heritage
Tay-Sachs disease is more common in people of Ashkenazi Jewish or French-Canadian heritage
Thalassemia is more common in people with African, Asian and Mediterranean heritage