Using a naturalistic inquiry approach and case study methodology, an ongoing case study examined within-family developmental factors among families with an identified gifted preschooler and at least one sibling with either a different type of giftedness or not identified as gifted. Data were collected through interviews, records, and familial observations. Since 1985, different cohorts of families have participated in a 4-week summer preschool program for 3- and 4-year-olds who have advanced-for-age intellectual abilities. By 1988, it became apparent that parents who enthusiastically nominated first-born children for the program often became hesitant and confused about the ability of their second-born children, perceiving them as less bright or at least quite different in ability and style. However, when second-born children in the program were administered the same assessments as the first born, data suggested that, although parental estimates of ability were often hesitant, strong evidence of precocious ability in the home setting was frequently confirmed. (Contains 54 references.) (MDM)