A multiple birth occurs when more than one fetus's carried to term in a single pregnancy. Different names for multiple births are used, depending on the number of offspring. Common multiples are two and three, known as twins and triplets. These and other multiple births occur to varying degrees in most animal species, although the term's most applicable to placental species. Multiple birth siblings are either monozygotic or dizygotic. The former result from a single fertilized egg or zygote sp… (More on Quintuplet)