There are horror movies that are not at all good, but for some incomprehensible reason they are world famous and extremely popular. Good for them, I guess. But the opposite exists as well. There are some horror pearls out there that are quite good, but for equally incomprehensible reasons, nobody has ever heard of them, and you must really seek intensively if you want to see them. The Mexican oddity "The Sheriff's Strange Son" sits in this category, sadly.
I honestly can't fathom why this gem is completely unknown. Bad marketing, maybe? Or maybe - and most likely - audiences (and especially American audiences) simply weren't interested anymore in westerns during the early 80s, regardless of featuring horror elements or not. It certainly isn't a bona-fide masterpiece, but what I can guarantee is this: it's a compelling and thoroughly uncanny tale full of original ideas and genuine suspense!
"The Sheriff's Strange Son" features plot elements to make all horror fan mouths' water! A little village struck by a plague, the predicament of the Antichrist's birth during a lunar eclipse, Siamese twins locked up in their room for seven years by their father/Sheriff, unorthodox surgeries, executions at the gallows, ... There are enough ideas for a couple of movies, in fact. I don't even know why it's a western, since the story also easily could have worked in a present-day setting as well, but it definitely adds a unique flair to the film. The kid playing both Fred and Eric is creepy, especially when he claims - via the body of Fred - to be Eric; - the weaker but nevertheless vengeful brother who died when his selfish father instructed the doctor to surgically separate the conjoint spine. Great ending, too!
PS: I discovered "The Sheriff's Strange Son" via "Evil Seeds", a book put together and edited by Vanessa Morgan, and a must-have in case you are even slightly fascinated by horror movies featuring evil children!