Background In China, esophageal squamous cell carcinoma (ESCC) and gastric cardia adenocarcinoma (GCA) share susceptibility loci, but different rates of multiple primary cancer and male/female ratio suggest the proportion of familial cancer is not equal. Methods The percent of cases with a positive family history, median onset age, rate of multiple primary cancer, and male/female ratio associated with upper, middle, lower third ESCC and GCA were compared to reveal the proportion of familial cancer. The 7267 subjects analyzed constituted all ESCC and GCA cases in whom the cancer was resected with cure intention between 1970 and 1994 at the 4th Hospital of Hebei Medical University. Results A positive family history for cancer was most often associated with the multiple primary ESCC and/or GCA cases, e.g. with 42% of the males and 59% of the females. For upper, middle, lower third ESCC and GCA, the percent of cases with a positive family history decreased by 38.5%, 26.3%, 26.5%, and 11.2% in males (P<0.000) and 25.0%, 22.3%, 23.9%, and 9.8% in females (P<0.0001). Median onset age increased from 49, 52, 55, to 56 years old in males and from 50, 53, 55, to 56 years old in females ( both P<0.0001) for upper, middle, lower third ESCC and GCA. Male/female ratio increased from 2.2, 2.1, 2.2, to 6.2:1 for upper, middle, lower third ESCC and GCA (P<0.0001). For upper, middle, lower third ESCC and GCA, the percent of multiple primary cancers decreased from 21.2%, 2.3%, 2.2%, to 1.5% in males and from 14.3%, 2.4%, 3.4%, to 3.1% in females. The preponderance of males, smoking, drinking, or onset-age >= 50 years was significantly higher in GCA than in ESCC, and the difference in the rates of multiple primary cancers between the preponderant and the non-preponderant cases was significant in GCA, but not in ESCC, suggesting non-equal requirement for genetic susceptibility when environmental hazards did not exist. Conclusions The proportion of familial cancer in upper gastrointestinal carcinomas decreases by the priamry site of upper, middle, lower third esophagus and gastric cardia. Considering familial and sporadic cancers differ in preventability, screening strategy and recurrence, our findings have basic and clinical implications.