It sounds like your Dad may be an alcoholic and that your Mom really doesn’t know what to do about it. Alcoholism is a disease that affects the mind, body and spirit of the alcoholic. Alcoholics are not “bad” people. In fact, many people suffering from the disease of alcoholism are really good peoples who are responsible, loving, kind family members when they are not drinking. People who do not have alcoholism can drink and not have to go overboard. Alcoholics are unable to stop drinking once they start. This has to do with differences in brain chemistry between alcoholics and non-alcoholics as well as other factors.
The truth is that once your Dad takes his first drink, he loses control over how much he will drink or how he will act when he gets drunk. Even though it seems like Mom should be able to stop or control how much Dad drinks, I bet she has tried to do this many times and not succeeded. She does not have the power to stop his drinking no matter what she says or does. All she can really do encourage him to get help and get help for herself and give you resources that can help you and your brother and sister cope with Dad’s drinking. Fortunately, there really are ways to help your family heal and find recovery.