Fraternal twins, also known as dizygotic twins, occur when two separate eggs are fertilized by two different sperm cells during the same pregnancy. This results in two genetically unique siblings who share about 50% of their genes, similar to any other siblings born at different times
. Key characteristics of fraternal twins include:
- They develop from two different eggs and two different sperm.
- They have separate placentas and umbilical cords (dichorionic).
- They can be the same sex or different sexes.
- They often look different, but sometimes may appear similar.
- Their genetic similarity is no greater than that of regular siblings
Fraternal twins are the most common type of twins, making up about two-thirds of all twin births. The likelihood of having fraternal twins can be influenced by factors such as maternal age and fertility treatments
. In summary, fraternal twins are essentially siblings who happen to be born at the same time, each developing from a separate fertilized egg during one pregnancy.
