A twin is one of two offspring produced in the same pregnancy. Twins can either be monozygotic ("identical"), meaning that they develop from one zygote that splits and forms two embryos, or dizygotic ("fraternal"), meaning that they develop from two eggs, each fertilized by separate sperm cells.
The twin birth rate in the United States rose 76% from 1980 through 2009, from 18.9 to 33.3 per 1,000 births. The world's highest rates of twinning are found across Central Africa, where there are 18-30 twin sets (or 36-60 twins) per 1,000 live births.
What most people don’t know is that there are actually seven different types of twins: Identical, Fraternal, Mirror-Image, Polar Body (Half Identical), Mixed Chromosome, Superfecundation, and Superfetation.
If you’d like to see the characteristics of each, make sure you check the source link.
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