Twins are a curious thing in Equestria. Even if they may technically be identical, it’s possible for the mane and coat colors of one twin to completely contrast the other though this is not always the case. Identical twins may also often have very similar, or sometimes identical, cutie marks. Commonly, cutie marks of identical twins that vary in design will seem to ‘fill in’ for each other as if they were parts of a whole. Because of this, twins share an immense bond between each other and often work side by side.
I actually really like this concept..
I might use the idea within my RP universe..