For years, the man, identified as Carlos RR, was allegedly kept locked in the tiny three-square-metre room in his family home near Seville, Spain, and made to sleep on a filthy mattress surrounded by his own excrement.
Police have arrested the man's brother, 76, and sister, 61, for the alleged imprisonment of their younger brother who suffered severe brain damage, according to local news reports.
The man's mental disabilities stemmed from an undisclosed incident when he was "very young", according to Spanish-language news oulet El Pais.