PROJECTED ACCRUAL: This study will accrue 1,000 patient-sibling pairs for breast cancer. After 18 months, another 1,000 patient-sibling pairs will be accrued for breast cancer. Therefore, up to 2,000 patient-sibling pairs will be accrued over 5 years. (Feasibility of accruing pairs for lung, colon, and prostate cancer is being assessed.)