Site: nolo.com
... U.S. citizens can, under federal immigration law, petition for (sponsor) their foreign-born brothers ... Citizen Sponsoring a Half-Brother or Half-Sister
A U.S. citizen who is age 21 or older may, by law, ... The definition of sibling in U.S. immigration law includes people who were the children of at least one ... , Sections 101(b)(1) and (b)(2) of the Immigration and Nationality Act or I.N.A, or 8 U.S.C. ... § 1101(b)(1) and (b)(2).), which requires that the child have not yet reached the age of 18 when ...