One of the first things pregnant people wonder is whether or not they'll have twins. According to the Centers for Disease Control and Prevention (CDC), the likelihood of a pregnant person having twins ...

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 ...

Mono-mono twins are an incredibly rare type of identical twins who share both a placenta and an amniotic sac. While this makes for a high-risk pregnancy, advances in monitoring and treatment have ...

When you hear twins, it is common to imagine two babies who appear the same. However, not all twins share similar physical features. Indeed, some look exactly alike, but others may have different ...

There are two types of twins: fraternal twins and identical twins. Identical twins are born when an egg is fertilised by a single sperm and two identical twins with the same sex and DNA are produced.

Twin estrangement starts with unresolved anger between twins in childhood. Perhaps one twin is favored over the other twin for parental personal reasons. Another explanation is that one twin is in ...

The Science of Siblings is a new series exploring the ways our siblings can influence us, from our money and our mental health all the way down to our very molecules. We'll be sharing these stories ...