A child can also obtain U.S. citizenship through parents after the child’s birth and before the age of 18. Derivative citizenship may be established after birth but before the age of 18. If you have a parent that became a U.S. citizen after your birth and met a few other requirements, you could be a U.S. citizen automatically through this path.
Requirements
To become a citizen through parents after birth, the following four requirements must be true at the same time:
– At least one of the child’s parents is a U.S. citizen by birth or naturalization;
– The child is under 18 years of age;
– The child is a lawful permanent resident;
– The child is residing in or has resided in the United States in the legal and physical custody of the U.S. citizen parent.
When all of the conditions are met, citizenship is recognized. They can happen in any order, but they all must be true at the same time. Most often, derivative citizenship happens when a permanent resident child lives with at least one permanent resident parent in the United States and that parent naturalizes. As mentioned, American citizenship through parents is acquired automatically. However, the beneficiary needs documentation as evidence of citizenship status.
As long as these requirements were met at some point in time, the applicant may request a certificate, even if the applicant is now over the age of 18.
Request a Certificate
Again, to establish your status as an American citizen, you’ll need to request a Certificate of Citizenship by using Form N-600, Application for Certificate of Citizenship. You must submit supporting documents that prove the three conditions above were true simultaneously

