Posted by: guchcha chor May 16, 2012
Green card application through brother who is US Citizen
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 Here is what I found in USCIS. I think it's close (or same) to your situation:

Can my sibling come to the United States to live while the visa petition is pending?

There is no avenue for your sibling to enter the United States prior to immigration on the basis of a pending Form I-130. 
In most instances, the beneficiary of a pending or approved immigrant visa will not be eligible for a nonimmigrant visa,
although certain exceptions may apply.



http://www.uscis.gov/portal/site/uscis/menuitem.eb1d4c2a3e5b9ac89243c6a7543f6d1a/?vgnextoid=b8c93e4d77d73210VgnVCM100000082ca60aRCRD&vgnextchannel=b8c93e4d77d73210VgnVCM100000082ca60aRCRD
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