A Green Card holder can sponsor their spouse and children (married or unmarried). To start the process, file an I-130 for each family member you wish to sponsor. There will be a visa wait time which can range depending on the family relationship (spouse/minor child/unmarried adult child/married adult child) and country of origin. After a visa becomes available, you apply through the Department of State for your family’s visas, complete interview at consulate abroad and they are able to come into the US as Green Card holders. Work with an immigration attorney to strategize the fastest ways to bring your family through the legal processes available. Also, if you become a US citizen midway through your family petitions, it can sometimes advance (and sometimes delay!) the visa wait times as it will change your categories - so make sure you speak to an attorney before you become a US Citizen. Best of luck!