Living in a different country than one's child, whatever their age, can be very hard for a parent. Thus, one thing a parent who is a U.S. citizen who has a child who is not a U.S. citizen may strongly desire is to get a green card for their child so their child can live with or near them here in the United States.
Very generally, children of U.S. citizens have green card eligibility. However, one should understand that the definition of a "child" is a very distinct concept under immigration law. What rules and processes apply to efforts to get a green card can vary depending on what particular classification the child has under U.S. immigration law. What classification a non-citizen child of a U.S. citizen has depends on the child's age and marital status.
When a child of a U.S. citizen is under the age of 21 and unmarried, they are classified as an immediate relative. If, however, a child of a U.S. citizen is married or is over 21, they are instead classified as a relative that falls under the "family preference category".
Whether a child is classified as being an immediate relative or in the family preference category has some significant implications. For one, it can impact how easy it would be to get a green card for the child. This is because, while the U.S. puts no limit on how many "immediate relative" visas it gives out per year, it does put limits on how many "family preference category" visas are issued. Also, the processes for seeking out a green card can be different between a child who is classified as an immediate relative and a child who is classified as being in the family preference category.
When seeking a green card for a child of a U.S. citizen, understanding what specific rules and processes apply is very important. Immigration attorneys can help parents who are trying to get a green card for their child and children of U.S. citizens who desire a green card navigate the green card process.
Sources: U.S. Citizenship and Immigration Services, "Green Card for an Immediate Relative of a U.S. Citizen," Accessed Oct. 27, 2015
U.S. Citizenship and Immigration Services, "Green Card for a Family Member of a U.S. Citizen," Accessed Oct. 27, 2015