How much does family history affect breast cancer risk?
In your case you have a very high chances of having breast cancer. These chances would be even higher in case any of the male members of your family tree had prostate cancer or breast cancer. In addition to breast cancer the genes are also responsible for ovarian cancer. You need to start getting examined annually latest by age of 22 (5 years prior to the youngest member having cancer) though some doctors recommend 10years prior. It would also be good if you could undertake a genetic study for the likely genetic mutations at the earliest, which would include BRCA 1 and 2 and also some other known mutations. All the best and get in touch with your doctor.