Question: I became a permanent resident through marriage. Now that I have my permanent green card can I petition for a green card for my brother or sister?
Answer: No. Only a U.S. citizen age 21 or older can petition for a brother or sister.
Immigration laws limit which relatives a U.S. citizen or permanent resident can sponsor. Included are the spouse of a U.S. citizen or permanent resident, all children of U.S. citizens no matter their age or marital status, the unmarried children of any age of a permanent resident and the brothers and sisters of U.S. citizens.
Unfortunately, once you petition for your sibling, it could take decades for him to get his green card. If your parents are alive and want to immigrate to the United States, you may be able to get your brother or sister to the United States faster if your parents petition for them.