Obviously, these failures cover a spectrum. The parent who beats a kid insensibly on a regular basis registers differently on the disappointment-meter from the one who doesn't deliver a pony for Christmas. Probably the vast majority of families fall between these two poles. Nevertheless, I believe that every tribe has to accommodate a wide range of behavior from its members. Illness and death, which we're taught in this country to view as aberrant, actually afflict us all.
Depression hits everybody from time to time.
The current figures on alcoholism vary, but I heard a lecture once where someone claimed that five percent of the population consumes ninety percent of the liquor sold. You can bet that segment of the population causes considerable strain on those near and dear. When people suffer their relationships usually suffer as well. And we all suffer because, as the Buddha says, that's the nature of being human and wanting stuff we don't always get. Still, their rates of divorce and alcoholism are up like ours.