Kramer conducted research on 20 sets of twins, both fraternal and identical. What she found was a relationship unlike almost any other. "They say things like, "Life partner,'" Kramer says.

Identical twin sisters Bridgette and Paula Powers spoke in sync and mimicked each other's gestures during an interview about ...

and identical twins were more likely to share allergies than fraternal (nonidentical) twins. Identical twins share 100% of their genes, while fraternal twins only share about 50% of their genes ...