US immigration law already has strict quotas for siblings. The backlog for sibling greencards stretches back decades. So sponsorship is possible in theory, but

US immigration law already has strict quotas for siblings. The backlog for sibling greencards stretches back decades. So sponsorship is possible in theory, but little used in practice. The main sponsorship that's currently easier in the US than other countries is parents of citizens, who are considered immediate relatives and are not subject to quota.