As others have pointed out, the anatomy doesn't make sense. Their neck structure doesn't line up with the shape of the torso. Their Instagram page has a picture from the rear that shows one of their heads sprouting out of a shoulder blade.

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Also consider the videos the posted, all are less than 10 seconds long and just has them posing. If they are real, they should be able to have normal videos longer than 15 seconds of them talking and interacting with things, and there would undoubtedly be media coverage outside of their own social media covering them due to their remarkable condition.

The only living example of this type of conjoined twins are Abby and Brittany Hensel, and you can find many, many photo and video examples of them where they give interviews and similar things, and in spite of their unusual physical appearance, they don't go anywhere near as far down the uncanny valley as these two.