It is well known that U.S. citizens and permanent residents can sponsor certain categories of relatives and get them permanent resident cards (green cards). To sponsor their relatives, they must file the USCIS Form I-130, Petition for Alien Relative.
If you are a U.S. citizen, you can file Form I-130 for your parents, spouse, children and your siblings. But if you are a permanent resident, you cannot file this form for your parents and siblings; you can only help your spouse and children get green cards.
You can file this form for a relative who is living abroad or for someone who is in the U.S. as a non-immigrant. If the relative you are sponsoring is abroad, he or she must go through consular processing to get an immigrant visa. Once your relative successfully goes through this process, he or she will be issued an immigrant visa with which he or she can travel to the U.S. In case your relative is in the U.S. as a non-immigrant, he or she can go through a process called adjustment of status. People who go through this process need not return to their home countries to get immigrant visas. They can get green cards while in the U.S.
If you are a U.S. citizen and if you have filed Form I-130 for your immediate relative who is abroad, your relative will be permitted to apply for an immigrant visa soon after the approval of Form I-130. But if you have filed this form for a relative who belongs to the preference category, your relative will have to wait until a visa number in his or her particular category becomes available. Only after the priority date becomes current, he or she can file an application for an immigrant visa, at an overseas U.S. embassy or consulate. This also applies to the relatives of green card holders who do not belong to the immediate relatives category.
Your immediate relative who is in the U.S. can file Form I-485, Application to Register Permanent Residence or Adjust Status, for adjustment of status when you file an immigrant petition for him or her. But this does not apply to the relatives classified under the preference category. They need to wait until the immigrant petitions filed on their behalf are approved. They can file applications for adjustment of status only after visa numbers become available to them. Till then they need to maintain their non-immigrant status. Similarly, if you are a green card holder, your relative must wait until a visa number becomes available after which they can file an application for adjustment of status.
If you wish to sponsor more than one relative, you will have to file separate applications for each relative you wish to sponsor. You will need to complete the two pages long form and file the form with the $420 form filing fee, for each relative.