Twin births are pretty common events that happen these days. There are two different types of twins and they are identical and non-identical or fraternal twins. In the case of identical twins, the egg, when fertilized, is split into two different halves. In this case, the egg is fertilized by a single sperm cell and after splitting, both the embryos will share the same chromosomes of the birthing as well as the non-birthing parent. These twins are assigned the same sex during birth and also share the same genetic characteristics as well. However, there is a chance that these twins might not have the same physical characteristics.