It's a fact. The two haves have the pointy broken bits at the same spots, it's identical. So they can't be conjoint twins since the pieces would not fit together ala a puzzle.

Therefore I propose the one twin killed his conjoint brother and then cloned himself to cover up the murder.

(Coincidentally that will be the plot for detective novel set in the year 2065 I am sure to write this year if Hollywood doesn't steal it first.)