Identifying familial linkages in a phenotypic data warehouse can be valuable in cohort identification, and beginning to understand interactions of diseases among families. The goal of the Familial, Associational, & Incidental Relationships (FAIR) system is to identify an index set patients’ relationships through elements in a data warehouse. Using a test set of 500 children, we measured the sensitivity and specificity of available linkage algorithm (e.g.: insurance id and phone numbers) and validated this tool/algorithm through a manual chart audit. Sensitivity varied from 16% to 87%, and specificity from 70% to 100% using various combinations of identifiers. Using the “i2b2” warehouse infrastructure, we have now developed a web app that facilitates FAIR for any index population.