Source: http://immigration-lawyer-us.com/children/
Timestamp: 2019-04-18 15:27:02+00:00

Document:
– A child adopted who is under the age of 18 and the natural sibling of an orphan or adopted child under the age of 16, if adopted with or after the sibling. The child must also otherwise fit the definition of orphan or adopted child.
The immigration law defines a “son or daughter” as a person who was once a “child” but who is now either married or over the age of 21.
1) You must obtain USCIS approval of an immigrant visa petition that you file for your child, son or daughter.
2) The State Department must then give your son or daughter an immigrant visa number, even if he or she is already in the United States. If you are a U.S. citizen and the child is both under 21 years of age and unmarried, a visa number is not required.
3) If your child or son or daughter is outside the United States, he or she will be notified to go to the local U.S. consulate to complete the processing for an immigrant visa when one becomes available. If your child or son or daughter is legally in the U.S. when an immigrant visa number becomes available (or if one is not required), he or she may apply to adjust status to that of a lawful permanent resident.
The Immigration and Nationality Act is a law that governs the admission of all immigrants to the United States. For the part of the law concerning immigrant status for children, sons, and daughters, please see INA § 202, INA § 203 and INA § 204. The specific eligibility requirements and procedures for qualifying for immigrant visas and permanent residence are included in the Code of Federal Regulations (CFR) at 8 CFR § 204.1, 8 CFR § 204.2, and 8 CFR § 204.3.
– A U.S. citizen’s unmarried, minor child is considered an immediate relative, does not need a visa number, and is eligible to receive an immigrant visa immediately. Otherwise, sons and daughters of U.S. citizens will be eligible for a visa when their priority date is listed on the Department of State’s Visa Bulletin .
If your unmarried, minor child was admitted or paroled into the U.S., he or she may file an Application to Register for Permanent Residence or Adjust Status, at the time you file your Petition for Alien Relative.
– A lawful permanent resident may not petition for a married son or daughter.
If you had children before you became a permanent resident and you did not immigrate as an immediate relative of a U.S. citizen, your unmarried, minor children may be eligible to receive following-to-join benefits. This means that you do not have to submit a separate USCIS Petition for Alien Relative for your children, and your children will not have to wait any extra time for a visa number to become available.

References: § 202
 § 203
 § 204
 § 204
 § 204
 § 204