I mean mirror image twins. Approximately 25% of all identical twins are mirror image twins. Or mirror twins, or opposite twins. There are a few different ter

I mean mirror image twins. Approximately 25% of all identical twins are mirror image twins. Or mirror twins, or opposite twins. There are a few different terms for the same phenomenon. The exact cause is unknown but it's theorized that mirror image twins happen when the zygote splits a few days later than 'normal'.