The present study examined to what extent regular drinking of fathers, mothers, co-twins, siblings, and friends was related to adolescent regular drinking in three age groups: 12-15, 16-20 and 21-15-year olds. The sample consisted of 3760 twins (1687 boys, 2073 girls) with a mean age of 17.8 years. Data were based on twins' self-reported alcohol uses and reports about siblings' and friends' alcohol use, and on parents' self-reports. Results showed that generally in each of the three age groups, regular drinking of same-sex co-twins and friends posed the highest risk for regular drinking. Age differences indicated that these risks decreased with age. Irrespective of age, regular drinking of fathers and mothers posed the lowest risk. Findings were generally the same for males and females.