At first sight, you might—or might not—imagine that these are portraits of two sisters, who could well be twins (but surely not identical twins):
In fact, these two reconstructed images are based upon a unique original photo of a single individual whose facial features are rather asymmetrical. To form each image, one half of the woman's face has been copied and then combined with a mirror image of itself.
Click the double-portrait to access the website of the photographer, Julian Wolkenstein, who presents several samples of this technique. It's a pity (I feel) that he doesn't show us the original photos.
In reality, many ordinary-looking human faces turn out to be quite asymmetrical when examined closely.