In general, it is difficult to pursue permanent residency from within the U.S. after entering the U.S. as a visitor.
In general, it is only even conceivable if the individual is being sponsored for a green card by an immediate relative (i.e. spouse of a U.S. citizen, parent of adult U.S. citizen, child under 21 years of age of U.S. citizen).
It is generally not possible to pursue a green card through other family relationships because the process is too long and the visitor would end up overstaying.
Applying for a sibling falls under the 4th preference category and that process can minimally take 10 years depending on nationality. See:
http://www.travel.state.gov/visa/bulletin/bulletin_5542.html
Regards,
Andrew M. Wilson, Esq.
Serotte Reich Wilson, LLP
www.srwlawyers.com
awilson@srwlawyers.com
Answered on Sep 01st, 2011 at 7:27 PM