Pathologic hoarding does seem to be more common than I had supposed. I've heard that up to five percent of Americans are affected. Certainly, awareness of hoarding has grown recently thanks to television shows on the subject. Academicians have also been studying this type of behavior, characterized by the excessive collection and inability to part with of all kinds of stuff, sometimes including dozens, even hundreds, of pets living in crowded, unsanitary conditions.
Hoarding hasn't yet been classified as a distinct mental health problem, although it is listed as a symptom of obsessive-compulsive disorder. There certainly appears to be an element of compulsion involved in accumulating clutter and being unable to organize all the stuff or throw it away. This is summarized in an old New England story about going through the attic of an elderly hoarder, and finding a box labeled "string too short to save."
When I moved recently, I was surprised at the amount of stuff I had accumulated over the years. But hoarding goes far beyond the normal pile-up of things we all store or put aside because we aren't ready to throw them out or think we may need someday. Hoarding even goes beyond "pack rat" behavior, and there may be a genetic component to it. (Hoarding runs in some families.) Hoarders feel emotionally connected to their hoards. I've read that they feel safer when surrounded by all their clutter, even though some or most of what they've been keeping and acquiring is useless, or even dangerous as it may be unsanitary or a fire hazard.
Many hoarders don't see anything wrong with their behavior, or feel powerless to change their behavior if they do. A family member or friend may have to meet with a mental health provider first, if treatment seems indicated, but that may not help if the hoarder doesn't recognize there is a problem or isn't willing to address it. In some cases, cognitive behavioral therapy may change the hoarding behavior, and occasionally, medication is useful, particularly the SSRI antidepressants. These drugs can work well for obsessive compulsive disorder, but based on what I've read, they're not as effective for hoarding.
As a start, I would suggest trying to persuade one or more of your relatives to consider psychological treatment. There's no way to know whether or not it will work until you try.
Andrew Weil, M.D.