The Wilsons were the typical all-American alcoholic family. While I've never read anywhere that Murray was an alcoholic, he was an adult child of an abusive, violent alcoholic. I believe it's very likely Murray was an alcoholic. I read in one bio that Audree Wilson was.
The roles of the kids were so typical: Brian was the family hero, Dennis the scapegoat, Carl the lost child.
The Hero: Alcohol bestows this role onto the individual whose accomplishments compensate for the alcoholic's behavior. The child excels in academics, athletics, music or theatre. His/her deeds assure the family that their definition is more than alcohol. Purpose: The hero role raises the esteem of the family. Negative Consequence: The hero does not receive attention for anything besides an achievement; therefore, inner needs are not met. He/she loses the ability to feel satisfied by whatever feat he/she has manifested.
The Scapegoat: The family assigns all ills to the person who harbors this role. For example, they may tell this person that, "Mom would not drink so much if (Scapegoat's name) were not always in trouble. The child has issues with authority figures as well as negative consequences with the law, school and home. Purpose: The scapegoat puts the focus away from alcohol thereby allowing the alcoholic to continue drinking. This role may seem strange in purpose. However, if there were no scapegoat, all other roles would dismantle. He/she allows others a pretense of control. Negative Consequence: Alcohol is not identified as an issue. Often, the scapegoat is identified as 'The Problem.'
The Lost Child: As the title suggests, the lost child disappears from the activity of the family. Favorite places for the lost child are in front of the T.V. as well as in his/her room. Due to the sedentary lifestyle , a lost child tends to have issues with weight. Purpose: A lost child does not place added demands on the family system. He/she is low maintenance. Negative Consequence: The lost child sees much more than is vocalized. The family reduces its depth in not listening to what the lost child thinks and feels.
http://www.essortment.com/all/alcoholismin_rery.htm