What makes twins fraternal? Find out how much these siblings share from conception on, and how similar or different they might be.

Kim Perell says it was hard growing up with a twin sister. She encourages her twins to be individuals and not compare ...

Find out everything you've always wanted to know about identical twins – from how they form to what makes them unique.

But now, a new study has found that genetics determines how much babies cry. That means we may not have much control over it, no matter how much swinging and singing we try.

Fraternal (dizygotic) twins, who come from two separate eggs, can be hereditary, especially if the mother has a tendency to release more than one egg at a time. Identical twins usually occur randomly.

Identical, or monozygotic, twins develop from the same fertilized egg that splits into two. These twins are the same sex and share the same genes. Sometimes called paternal twins, ...

Identical, or monozygotic, twins develop from the same fertilized egg that splits into two. These twins are the same sex and share the same genes. Sometimes called paternal twins, identical twins ...

The author (not pictured) married an identical twin and had fraternal twins. Courtesy of the author I had an emergency C-section and gave birth to my twins early at 35 weeks.

So identical twins, if their breast cancer is due to an inherited predisposition in a mutation in one of these genes that's been identified, then they would be at significantly increased risk ...