Who can you petition for?
If you are a US Citizen you can petition for: your spouse, fiancé(e), children, parents and siblings.
If you are a permanent resident (green card holder) you can petition for your spouse and unmarried children.
Some of the family members that qualify for immigration benefits are subject to numerical limitations. The waiting time varies depending on the preference category the family member follows into.
Sometime when an immediate relative is present in the United States, a petition for a relative and his or her permanent residence application can be filed together.