Newly Diagnosed

I'm about to go the genetic counselling route as well ( not sure exactly when) and not sure what they're going to be able to tell me.  My only sibling died got bc at 32 and died at 45 but other than that, cancer is further afield that I know of.  Due to the generations being totally screwed up in my family, I don't know what the primary causes of many of the ailments were.  Eg. I know my auntie was addicted to medicinal morphine but why?