This is for you Ruez
Children of alcoholics are four times more likely than other children to become alcoholics, according to the American Academy of Child & Adolescent Psychiatry, but environmental factors could be a factor in many of those cases.
Family, twin and adoption studies have shown that alcoholism definitely has a genetic component. In 1990, Blum et al. proposed an association between the A1 allele of the DRD2 gene and alcoholism. The DRD2 gene is the first candidate gene that has shown promise of an association with alcoholism (Gordis et al., 1990).
A study in Sweden followed alcohol use in twins who were adopted as children and reared apart. The incidence of alcoholism was slightly higher among people who were exposed to alcoholism only through their adoptive families. However, it was dramatically higher among the twins whose biological fathers were alcoholics, regardless of the presence of alcoholism in their adoptive families.
Heres the link
http://alcoholism.about.com/cs/genetics/a/aa990517.htmI though everybody knew about this