The Minnesota Center for Twin and Family Research (MCTFR) is primarily composed of two studies; the Minnesota Twin Family Study (MTFS) and the Sibling Interaction and Behavior Study (SIBS). Both projects are longitudinal research studies including twins, siblings, and parents. Over 9800 individuals have contributed to these exciting projects! By studying twins and siblings and their families, we can estimate how genes and environment interact to influence character, strengths, vulnerabilities and values.