Am I eligible to join the Registry?

Can my twin and I join if we are fraternal twins?

Yes! We encourage fraternal twins to join the Twin Registry. It doesn’t matter if you and your twin are the same sex or different sexes. As long as you are twins, we welcome you to join.

Can I join if my twin is deceased or not interested in joining?

Currently, we are only able to enroll you in the Twin Registry only if both you and your twin are willing and available to enroll. Some studies may permit only a single twin to participate, but enrollment in the Registry as a whole is available only to twin pairs. Therefore, we are unable to enroll you if your twin is deceased or not interested in joining.

Please let us know if you or your twin is not available or not interested in joining, so that we can remove you from our mailing list. You may contact us by email at, or call toll-free at 1.833.432.8720.

Can I join if I am not in contact with my twin?

Maybe. If you are not in touch with your twin but wish to join the Twin Registry, please return our brief enrollment survey and indicate that you are not in contact with your twin. We will then put your enrollment on hold. If we receive your twin’s information in some other way, we can then enroll you both in the Twin Registry. Your mother’s maiden name is helpful in matching you and your twin in our database. We will never share your information with anyone outside of the Twin Registry, not even with your twin or any other family members.

Can my twin who lives somewhere else still participate?

Yes! Some of our studies involve in-person visits, while others are conducted by telephone or through the mail. This approach allows twins to participate in studies no matter where they live. Some studies may provide additional compensation for travel time and costs, but this varies from study to study. If compensation for travel is provided by a study, we will give you the details when we invite you to participate in that study.

Can triplets or higher-order multiples join?

We are currently unable to enroll triplets or higher-order multiples in the Twin Registry.

Are we too old to join the Twin Registry?

Twins who are “senior citizens” are very valuable to research. Some studies do not require an in-person visit to Seattle, which can make it easy for older twins to participate from home.

Can I enroll my twin children?

Yes! We welcome twins of all ages to join! If you are a parent interested in enrolling your twin children, please click here for more information. For twins 12 and younger, parents will complete the questionnaire for both twins. For twins 13-17, twins complete the questionnaire themselves with parental permission.

On the twins’ 18th birthday, we will send them an invitation to continue their participation in the Registry as adult members.