What is it called when two different fertilized eggs develop into twins?

When two different fertilized eggs develop into twins, this condition is referred to as fraternal twins. Fraternal twins, also known as dizygotic twins, occur when two separate eggs are fertilized by two separate sperm cells. This leads to the development of two genetically unique individuals. Each twin inherits a different combination of genes from their parents, meaning fraternal twins can share some physical traits but are no more genetically similar than regular siblings.

In contrast, identical twins arise from a single fertilized egg that splits into two embryos, making them genetically identical (monozygotic twins). Polyzygotic is a term that could theoretically describe multiple zygotes, but it is not commonly used to specifically indicate twins. Thus, the concept of fraternal twins highlights the distinct genetic backgrounds that can exist even in twin siblings.