This study uses measurements of social background variables, mental ability, educational attainment, occupational status, and earnings among male, Wisconsin high school graduates and a random sample of their brothers to develop and interpret simple models of socioeconomic achievement. The study was designed to contribute to the data on the influence of education on social mobility. Maximum likelihood estimates for pooled samples of fraternal pairs from the Wisconsin Longitudinal Study where both brothers were interviewed (532 pairs) and where only one brother was interviewed (N=928) were obtained. No evidence was found that the effects of family background lead to bias in the effect of mental ability on schooling or in the effects of schooling on occupational status or earnings. These findings are confirmed by a reanalysis of another set of data on 346 fraternal pairs from Kalamazoo, Michigan. Family background was found to have a large independent effect on ability, schooling, and, to a lesser degree, socioeconomic attainment. Although the models used are simple, it is felt that they provide a useful framework for the development of more complete models and comparative analyses of family effects on offspring who differ in sex, age, or ability. Several tables display the data. (Author/CG)