Exploring the Bond Between Twins

Dr. Nancy Segal, who studies twins, discusses what the bond is like between twins, especially for those who are separated.
1:56 | 01/16/17

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Transcript for Exploring the Bond Between Twins
Gracie and Audrey who reunited on "Gma" after being separated at birth. This morning we have a look at what they can expect next. Two girls reunited at age 10 separated as babies in China and adopted into two different American families. It's really overwhelming. Reporter: Dr. Nancy Segal, a twin herself has been studying twins for decades. This will provide another piece, what contributes to human developmental progress. Reporter: So far she's found that twins are very much alike and now that they reunited what does their future hold. Many time when is they meet each other for the first time they will say they feel complete or something's been missing in their lives. Reporter: No better experts than these two, Sara and Selena, also adopted as babies to two separate American families in Tennessee and New York. I just feel really grateful, I think, overall. Reporter: Neither knew they were a twin but there were hints when the girls went too college. This other student approached me and he said, can I take a picture of you? You really look like someone I know from back home. That friend was Selena. He took her picture and sent it to our friends. We laughed it was sort of like, ha, ha, you have a twin at this other school. It wasn't until a few years later they talked on Facebook and realized more eerie similarities. Adopted from the same place at the same time. They even finished each other's tens. When we first had dinner there was a moment of like, whoa. Reporter: A DNA test confirmed their relationship in 2015, identical twins. We definitely like the same foods. We're very much "Lord of the ring" fans. Reporter: They have advice. I would say cherish that relationship.

This transcript has been automatically generated and may not be 100% accurate.

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