Although there are some rare exceptions, identical twins are almost always the same sex. Because identical twins occur when a single fertilized egg splits and forms two embryos, each embryo has the ...

About 3% of live births in the U.S. result in twins. Fertility treatments, age, and family history can influence the chances of having twins. Twin pregnancies carry higher risks but receive extra ...

We have all seen twins, some of us even have one! While whenever the word "twins" come to our mind, we think of fraternal or identical pairs. But did you know that there are many other types and ...

Fraternal or dizygotic twins develop from two different eggs fertilized by separate sperm; they generally share about 50 percent of their genes. Therefore, fraternal twins are essentially like typical ...