It is possible but not likely. It will take more than a decade for an immigrant visa to be available to your family. They will not immediately be able to seek adjustment of status. So long as your sister and her husband have ties to their native country, they should be admitted. You can read more about visitor visas at http://myattorneyusa.com/travel-visas.
Answered on Jun 16th, 2016 at 12:38 PM