Alcoholism is a desease that affects every family to a degree, as is drug abuse. I had grand uncles on both sides of my family who both had major drinking problems. One of them died of alcoholic poisening. I don't know what happened to the other.
I guess when you live in adverse poverty, drinking or drug abuse is a cheap way of taking a 'vacation' from all the squalor you have to live with. Most of the first generation Irish imigrants were poor, worked the lowest paying jobs for the longest hours, and lived in roach infested, rat infested and crime infested "shanties" that became seyonimous with being Irish. "Shanty" Irish they were called. They came here to escape persecution by the British only to find some here. Yet many perservered, and build great lives for themselvs.
I was very lucky, because niether of my parents drank. But for some of our neighbors on Drake street, it's a different story. I've seen entire families destroyed, completely decimated by cocane, heroin, methamphetimine and alcoholism. When crack cocane was introduced back in the 80s, many of them died.
It's a sad legacy that poverty leaves us, but then there are those of us who are lucky to have loving parents who cared more about us then taking that small "vacation" in a bottle.