From the outside, fraternal twins naturally have great differences in their faces. Identical twins may have identical bodies and faces, but certain aspects may be mirror-opposite. For example, one might be left-handed, the other right, and moles or birthmarks may appear on the opposite side of the two twins.
再說面相，異卵雙生子的面貌如同一般的兄弟姐妹，當然相差就很大了；而同卵孿生子外貌雖然會極度相似，但是在他們的形體上通常會有相反方向的對比。