Men whose mothers, sisters or daughters test positive for a cancer-causing gene mutation also have an increased risk of developing the disease but are unaware of that risk. Like their female relatives, fathers, sons or brothers can also harbor a mutation in the BRCA 1 or 2 genes. Male carriers of these mutations, more commonly called the “breast cancer genes,” face a 14 percent lifetime risk of developing prostate cancer as well as a 6 percent lifetime risk of developing breast cancer.