How to list children on green card?
When filing a green card application, you must list all your children, natural, stepchildren or legally adopted, who are under age of 21 and are unmarried, regardless of your present marital status with their parent and whether you're applying for green card on their behalf or not.
Do not list children that are already US citizens or have a status of US Legal Permanent Resident (for instance those who immigrated recently via Diversity Visa Immigrant Program).
Do not list married children or children over 21, as they do not qualify to receive a green card together with you.