The best replacement for identical twins is fraternal twins.

The best alternatives to identical twins are rated as following:
★★★★★  fraternal twins
★★★  fraternal
★  mirror twins
★  non identical twins
★  twins
  fraternal difference
  paternal
  non identical
  paternal twins
  mirror image twins
  girl identical twins
  maternal twins
  monozygotic twins

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Speaking about identical twins, one probably shouldn't forget about two placentas.

Other search terms related to identical twins and their ratings are:
★★★★★ two placentas
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