Unless I missed something the article does not actually say whether or not the brothers actually live together.
It also does not say whether the surviving brother is fully functional. A fair number of elderly people (and yes, most people would consider 72 'old' even now) are not thinking as clearly as they once were. Some are frankly demented.
If the brothers lived together and the surviving brother has intact memory then I'd say he almost certainly has a psychiatric disorder.
I don't understand how this could happen. IMO 72 isn't that old by today's standards.
Not Every Man Is His Brother's Keeper
LONDON (AP) ? Police are investigating the case of an elderly man who apparently didn't discover that his brother had died in their mobile home until 18 months later.
On Dec. 3, Herbert Silver, 72, called police to tell them of the "sudden death" of his 75-year-old brother, George. When authorities visited the scene, they found a decomposing body.
George's cadaver was found in his bedroom in the home in Fordingbridge, a town in southern England.
Police declined to comment Thursday about what might have happened, saying an inquest would be held about how Herbert Silver could not have noticed for so long that his brother was dead.
A post-mortem examination could not find a cause of death, but police ruled out suspicious circumstances.
The inquest is scheduled to begin on Feb. 19, a Hampshire police spokeswoman said on condition of anonymity.
http://www.foxnews.com/story/0,2933,110796,00.html

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