Leah Sullivan, 4, and Erin Sullivan reside in the Scottish village of Inverness. After their mother recognized a remarkable trait in the girls’ growth and behavior, the girls rose to fame. This phenomenon, according to Zoya, 42, is “two sides of the same coin.”

From how they split their hair to how they use utensils, Leah and Erin do everything exactly the opposite.

The sisters face different directions while they sleep in the exact same position. Leah typically stands to the left and Erin to the right in photos.

The girls appear to be looking in a mirror as they stroll and interact with one another. The twins are radically different from one another by nature as if they were meant to be a pair.

The phenomenon is referred to by experts as “mirror twins.” It is used to describe twins with distinctive traits like birthmarks, dominant hands, or other opposing features that match as if they were staring in a mirror. About 25% of all pairs of identical twins experience this phenomenon.

What causes some siblings to mirror one another is unknown. This is thought to occur when the egg divides later in the fertilization process.

Between 4 and 8 days after conception, one fertilized egg divides into two embryos, producing identical twins. Mirror twins are thought to be the result of the egg separating later, between nine and twelve days. But this theory has not yet been demonstrated by science.