The man who threatened to kill Michael Jackson believed he was married to Janet Jackson -- and law enforcement sources tell TMZ it was Janet that the man was obsessed over.
A law enforcement source tells TMZ the man also made threats to kill Janet and even showed up at the Jackson family home in Encino.
In his rambling letters, the man -- Frank Paul Jones -- says "The situation ... is centered around her confused sexuality." He goes on to say if she does not "overcome" her issue over sexuality, "I'm gonna try to kill every homosexual on the face of the earth. If I can't save my wife, they can't be saved."