I was born in South Korea, and adopted by an American couple. Recently, one of my sisters in Korea tracked me down and contacted me. We are eager to get to know one another again, and I would like to help her get a U.S. green card if she wants one. Can I do this as her sister?
Unfortunately, U.S. immigration law considers an adoption of a foreign child into a U.S. family to legally cut off all family relationship to the birth family. Adopted children cannot file visa petitions to help their siblings, parents, or presumably any other blood relations immigrate to the United States. Basically, you can legally have only one family.
You won’t find this spelled out in the immigration law – it says only “That no natural parent of any such adopted child shall thereafter, by virtue of such parentage, be accorded any right, privilege, or status under this Act.” (See Immigration and Nationality Act, at I.N.A. Section 101(b).) However, cases heard by the Board of Immigration Appeals (B.I.A.) and federal courts have extended this prohibition to siblings of U.S. citizens.
The policy behind this is to avoid situations where someone adopts a child from a foreign country as a means to eventually bring in the child’s entire family.
There are exceptions to this law, but they apply only to circumstances completely different from what you have described here – for example, if you had immigrated by some means other than family, and if your adoption had been terminated, thus ending your legal relationship to your U.S. parents.