Yes it is. Both my parents and a sister smoked and died of lung cancer. My only brother died of a massive heart attack at the age of 51. I have one sister left who smokes and has managed to out-live everyone else in the family. I'm the baby, and she'll probably outlive me. I've never smoked, but know that I could still contract some form of cancer.
I have friends who are twins (male and female). They are in their 60's. Their father died from prostate cancer. They have lost two sisters to breast and ovarian cancer, and a brother to stomach cancer. Another brother died of heart problems, and another brother survived esophageal cancer. Two of their nieces (daughters of one of the deceased sisters) have also suffered bouts of breast and ovarian cancer. The female twin tested positive for the cancer gene. She underwent a voluntary double mastectomy as her doctor told her, it wasn't a question of if she'd ever get the disease, but when. It's been 2-3 years now, and thankfully all is going well.
As a breast cancer survivor myself, I know that if diagnosed early a lumpectomy plus chemo and radiation is all that is needed as opposed to a mastectomy. Plus I’m taking a pill to suppress estrogen for the next five years. If she’s afraid of chemo it wasn’t that bad for me thanks to some expensive drugs that fortunately my insurance paid for. I just experienced some fatigue. I just think that a double mastectomy without a cancer diagnosis is premature and unnecessary.