Anyone know about adult adoption?

I don't know about how adopting a 18 year old child from foster care works, but I do know that they cannot get citizenship through being your legal child if you adopt them over the age of 16, unless you also adopt a younger sibling, but even then the adoption would have to have occurred prior to their 18th birthday.

The age 16 rule applies primarily in terms of getting an adoption visa, not getting citizenship. If you adopt a child who lives overseas and want to bring him/her to the U.S., the child must not have reached his/her 16th birthday at the time the I-600 or I-800 is filed; I-600 is filed for children in countries that are not party to the Hague Convention on international adoption, and I-800 is filed for children in Hague-compliant countries. The only exception is for children whose younger bio sibling has already been adopted by the same family. Now, if the child you adopt is under 16 and receives an IR-3 or IH visa to enter the U.S., then he/she will become a citizen automatically once he/she enters the U.S. and a certificate of citizenship will be sent to him/her. However, if the child receives an IR-4 visa either because both adoptive parents didn't see him/her before the final decree of adoption was issued overseas, or because the child did not receive a final decree of adoption overseas and came home under a decree of guardianship, for adoption in the U.S., the child becomes a U.S. citizen ONLY after he/she is adopted/readopted in the U.S., and you must apply for a certificate. If the child has reached the age of 16 and is ineligible for an IR-3, IR-4, or IH visa, and you apply for a regular dependent visa once he/she has lived with you overseas for two years, he/she is not eligible for automatic citizenship at all, and must be naturalized once he/she is in the U.S.If the child is already in the U.S., whether legally or illegally, the above rules aren't relevant. Technically, a child who is a citizen of another country must return to his/her birth country and must be adopted under the rules of that country, which may have its own rules regarding when a child stops being adoptable; with China, for example, children stop being adoptable at 14. However, that policy is often ignored. If the child is in foster care and legally available for adoption, you may adopt him/her, but that won't affect his/her citizenship status. About all you can do, if the child is in this country illegally, is to try to persuade the USCIS to avoid deporting him/her and to give him/her a permanent resident visa, which can, at some point, allow him/her to go through naturalization. Get a good lawyer, as you may need one. If the child is in the country legally, you can work with the USCIS to go through the naturalization process.Unfortunately, people who thought they were helping an illegal alien by adopting him/her have often found that the adoption really does not improve his/her chances of becoming legal or a U.S. citizen.Sharon