SIBLING DEVIANCE: IN THE SHADOWS OF MUTUAL AND UNIQUE FRIENDSHIP EFFECTS?* DANA L. HAYNIE The Ohio State University SUZANNE McHUGH SUNY-Albany zyxwvu Drawing on a large sample of genetically related pairs of adolescents from the Add Health, we examine the influence of sibling deviance on adolescents’ participation in minor deviance compared to the influence received from mutual friends (i.e., friends shared between siblings) and influence from unique friends (i.e,, friends unique to each sibling). Multivariate analyses that control for genetic relatedness using DeFries- Fulker regression (1985) indicate that after aspects of the shared and non-shared environment of siblings are accounted for, the heritability effect, capturing genetic relatedness in sibling deviance, is no longer sig- nificantly associated with deviance. The deviance of siblings’ unique friends accounts for a large portion of the heritability effect of sibling deviance. zyxwvut KEYWORDS: Siblings, deviance, peer influence, Defies-Fulker regres- sion. Sociology and criminology have a rich and extended history of examin- ing family and peer effects on adolescent deviance and delinquency. Research focusing on family effects has investigated parent-child rearing behaviors (e.g., parental discipline, parental supervision, parent attach- ment), family structure (e.g., the effect of living in a single-parent family, zy * We would like to thank Steve Messner and the anonymous reviewers for their helpful comments and suggestions. An earlier version of this paper was presented at the 2001 meetings of the American Society of Criminology. This research uses data from the Add Health project, a program project designed by J. Richard Udry (PI) and Peter Bearman, and funded by grant P01-HD31921 from the National Institute of Child Health and Human Development to the Carolina Population Center, University of North Carolina at Chapel Hill, with cooperative funding from 17 other agencies. Persons interested in obtaining data files from The National Longitudinal Study of Adolescent Health should contact Add Health, Carolina Population Center, 123 West Franklin Street, Chapel Hill, NC 27516-2524 zyxwv http://www.cpc.unc.edu/addhealth Direct correspondences to Dana L. Haynie, Department of Sociology, The Ohio State University, zyxwvutsr 300 Bricker Hall, 190 N. Oval Mall, Columbus, OH 43210. Email: haynie.7@osu.edu CRIMINOLOGY VOLUME 41 NUMBER 2 2003 355