Identical twins form once one egg has been inseminated by one sperm and therefore the fertilized ovum splits into two. This happens at the very earliest stage of development, once the fertilized ovum is no more than a cluster of a number of cells. Dividing this early in conception means that every baby has exactly the same genetic info as the other.
Identical twins can even occur once one a woman has undergone fertility assistance and has had one inseminated egg came to her womb. If this egg then splits into two, a uniform twin pregnancy may result.
Identical twins aren’t dependent on race, country or ethnicity. the percentages of getting identical twins are constant for each couple, in each pregnancy, where they live in the planet.
Around one in every three sets of twins born is identical, and the remaining 2/3 is of the non-identical variety