My father died from stomach cancer. My maternal grandmother died from bone cancer. My maternal aunt died from brain cancer. My mom had cervical cancer. My fraternal aunt died from bone cancer. My fraternal grandfather died from complications caused by a life long struggle with leukemia. There is probably more, but this is what I know about.
The medical profession once held that any cancer in your family put you at risk for getting it....earlier rather than later. These days the belief is that one is genetically predisposed to more specific cancers. Hence, my having prostate cancer is not necessarily the result of my forefathers and relatives having cancers.
What I know for certain is that I have experienced a few low-grade "pre-cancers" in the past, all of which were caught and treated early on because my doctors were on guard for my getting cancer. Had it not been for my family history, my doctors and I may not have been a diligent.
Still, it is wise to realize that medical science is ever changing. This is one reason it is known as the "practice" of medicine....they are just "practicing" in hopes of getting it right someday.