Research data show that 90% of the etiology of cancer is exogenous, and heredity accounts for a very small fraction of the etiology of tumors. With the exception of colon cancer, which evolves from polyposis coli, and skin cancer, which evolves from pigmented dry skin disease, most cancers are considered to have no clear relationship with genetic factors. For families in which several people develop liver cancer at the same time or first or later, perhaps common living conditions, such as shared exposure to a carcinogenic substance, are much more important than genetic factors. In other words, although liver cancer is not hereditary, there is a tendency for families to cluster. Members of a family in which a patient with liver cancer has occurred should be alert to this disease. Most scholars believe that liver cancer has a certain tendency to gather in families: 1. Vertical transmission of hepatitis B virus: Mothers who are infected with hepatitis B virus and become long-term virus carriers may transmit the virus to their newborns during or after childbirth. Because the newborn’s immune function is not yet sound, it cannot effectively clear the virus and form a persistent infection, resulting in chronic hepatitis, cirrhosis, and finally evolving into liver cancer. 2, the level of hepatitis B virus transmission: hepatitis patients with family members in close contact, such as one infected with hepatitis B virus, it is easy to unknowingly spill over to others. 3.Dietary habits and lifestyles among family members: There is another explanation for more than one person in a family to have cancer. The basic idea is that any cancer is the result of two mutations in the genes of cells. In patients with sporadic non-familial cancer, both changes occur after birth. In contrast, patients with familially predisposed cancers are already under attack by this cancer-causing factor before their mothers become pregnant. When they are born, the cells in their bodies already have a cancer-prone change, and after they are born, they are likely to develop cancer if they suffer another attack from cancer-causing factors. This is the famous “two strikes theory”.