If you know that you do not have your family's medical history then it is important for you to make sure you have regular check ups with your doctor. To watch your weight in case you might have a higher likely hood of diabetes, heart disease or obesity. But how will knowing that you have a family history of parkinsons change something for you? At this point I don't think there is something preventative you can do to avoid it. Since you don't know your risk for cancer make sure you get regular tests, ask for a mammogram earlier then women with no risk, get regular pap smears and eat right. Wouldn't that be what you would do if you had the genetic disposition anyway?
Maybe before you have children you might want to get tested to make sure you don't carry Tay Sachs or Sickle Cell, I think medical history can be overrated. Just try to be healthy.
Next, let me quick touch on your comment about "emotional connections aside." I don't know if you were adopted or in foster care for years but an adopted family can have the same emotional connection that a biological family can have. I am planning to adopt children and I will love them as much as if I have my own and I am positive that my family will do the same because I already know they do. My cousin married a woman who already had a four year old from a previous relationship. The little girl was a flower girl in my wedding, my grandmother brings her just as many toys as she does the ones who are "biologically" related to her. My cousin, her adoptive father, treats the girl like her own, I would expect to do the same with any adoptive children and I would expect no less from any family...
