FAMILY INFORMATION BIAS:
The flow of family information about exposure and illness is stimulated by, and directed to, a new case in its midst1. This bias is similar to, and arguably a specific type of, Recall Bias. Such that those with a disease are more likely to report that they were exposed to an important risk factor for the disease (in this case genetics), compared to those without the disease. This bias is defined based on data from a historical paper on arthritis, when the authors noted that those siblings with arthritis were more likely to report that a parent had arthritis (a positive family history) compared to those siblings without arthritis2. Also see: Information Bias, Recall Bias, and Proxy Response Bias.
References:
1. Sackett DL. Bias in analytic research. J Chronic Dis. 1979;32 (1-2):51-63. (Link to Reference)
2. Schull WJ, Cobb S. The intrafamilial transmission of rheumatoid arthritis. 3. The lack of support for a genetic hypothesis. J Chronic Dis. 1969;22(4):217-22. (Link to Reference)