If you are allowed to live legally in the United States (whether as a U.S. citizen, green-card holder, or almost anything else), chances are your foreign-born children are eligible to live here too. (Note that this article does not discuss the eligibility requirements for stepchildren and adopted children.)
In order to be eligible to live in the United States, your children will need to prove that you really are their parent. This article describes how the U.S. government might allow them (or you) to prove that relationship—depending on whether you are the child's mother or the child's father.
(See the U.S. Code of Federal Regulations at 8 C.F.R. Section 204.2(d).)
To prove a mother-child relationship, it is enough to submit evidence of a biological relationship, preferably in the form of an acceptable birth certificate. (This is assuming, of course, that the child has not been permanently adopted by someone else — such adoption would legally terminate any prior parent-child relationship.)
A birth certificate is usually acceptable if it was registered not too long after the child's birth and it includes, in addition to the child's date and place of birth, the names of the mother and the child (matching their names on other official documents), as well as evidence that the certificate was issued by the appropriate government authority of the child's country of birth (for example, the signature and seal of the appropriate local government official).
Sometimes, a birth certificate is not acceptable or available. (If, for example, you are a refugee from Somalia, it is possible that your child's birth record was destroyed during that country's civil war.) In such a situation, you should at least try to find out whether you can obtain from the government of the child's country of birth an official letter (often referred to as a "certificate of nonavailability") explaining why an acceptable birth certificate cannot be issued. Regardless of whether your attempts succeed or fail, however, be prepared to submit as many alternative documents as possible.
Alternative documents might include two or more affidavits of birth (sworn letters written by relatives or other persons with personal knowledge of the facts of a child's birth), as well as medical records, school records, and religious records (such as certificate of baptism issued by a church) showing the names of the mother and the child.
If alternative documents are not available or sufficiently credible (believable), the U.S. government might require that the mother and child obtain a blood test from a laboratory accredited by the American Association of Blood Banks (AABB). Such a test, though not routinely requested, would at least prove that the mother and child could be directly related. If it is requested of you, you should know that refusing to take the test would be interpreted as evidence of ineligibility, except if you do so for legitimate religious reasons. (The fact that the test is expensive is not reason enough.)
Finally, if none of the options above seems conclusive, the U.S. government may suggest that the mother and child obtain a DNA test from a laboratory accredited by the AABB. Such a test, though voluntary, would provide definitive proof of a biological mother-child relationship.
If you're seeking to prove a father-child relationship, providing a birth certificate with your name on it or other evidence of a biological relationship will not be enough by itself.
The U.S. government will certainly require you to supply such evidence of a biological relationship (remember that we're not discussing stepchildren or adopted children here). You can show your biological link to the child in the same way that a mother would, as described above, including by DNA testing. The main difference for fathers is that the names of both the father and the mother (not just the father) must appear on any acceptable birth certificate.
In addition, however, the U.S. government requires either evidence that the child was legitimated before he or she turned 18 or in the alternative, evidence of a personal relationship between the father and the child before the child turned 21.
A child born to unmarried parents is often referred to as "illegitimate" (or, under previous versions of the immigration law, "out of wedlock"). In such cases, the U.S. government will want to see further evidence that the child's father is truly his or her father. And even if the child was born to married parents, you'll need to prove this fact.
The simplest way for a child to be legitimated is if a marriage took place between the father and mother before the child turned 18. The best evidence of this marriage would be a civil marriage certificate issued by the appropriate government authority of the place where the marriage was celebrated.
If you are the child's father and you did marry your child's mother but are unable to obtain an acceptable marriage certificate, try to obtain a certificate of nonavailability in addition to alternative documents (including affidavits of marriage and religious records stating the date when the marriage was celebrated).
If, instead, you entered into a common law or customary marriage, and the law of the place where the marriage occurred does not require that such marriages be registered, then you should not need to worry about obtaining a certificate of nonavailability. The U.S. government will likely recognize your marriage if it was already recognized by the country where you celebrated it at the time you celebrated it.
If none of the above apply, you might be able to show legitimation based on having complied with some other rule (such as a requirement to obtain a court order) established by the law of the country where either the child or the father lived before the child turned 18.
However, even if your marriage was legal under the laws of the place where it was celebrated, the U.S. government will not recognize it if it is also in any way contrary to the laws of the United States (for example, if it involved polygamy or incest).
If you are the child's father and the child was born outside of marriage (out of wedlock), and you did not legitimate the child before he or she turned 18, then proving your father-child relationship will require evidence of a personal relationship (also referred to as a "bona fide" relationship) between you and the child.
For example, you might supply evidence that you lived with the child at some point, publicly treated the child as your own, and/or participated in the child's life—especially through financial and/or emotional support, but also through demonstrated concern for the child's well-being, school work, or religious instruction.
Be sure to include copies of any: receipts of money orders you sent to the child; insurance records naming the child as your beneficiary; letters exchanged between you and the child; and affidavits written by persons (perhaps your friends or your child's school officials) who know about the relationship.
As suggested above, proving a parent-child relationship can become a complicated and expensive process, particularly in cases where a birth certificate is either unavailable or insufficient. Your best bet is to consult an attorney in advance.