Every time I watch this video it cheers me up and makes me smile from ear to ear. These girls are so adorable. Twins are really a very interesting topic. No one really knows why an egg splits; technically it’s a malfunction of the normal development process. There’s no hereditary trait that influences a predisposition to having identical twins. Although there are families with a high incidence of identical twins, it is due to chance, coincidence or plain good luck. Identical twins represent about a third of all twins. Dizygotic twins are twice as common as monozygotic. The odds of having identical twins is about 3 in 1,000, whereas the birthrate for all twins is about 32.2 in 1,000. Identical twinning is not generally influenced by fertility-enhancing treatments, although monozygotic twins have been produced in pregnancies that were the result of such treatments. Birth rates for identical twins are consistent across populations; it is the same regardless of race, geography or maternal age.