If your sister is aged 21 or over, she can petition her parents, who will be in the Immediate Relative category with no wait for visa numbers. Her siblings cannot immigrate as her parentu2019s derivative beneficiaries, because the Immediate Relative category cannot have derivative beneficiaries. Her parent(s), once they enter the US, can immediately petition for their children, and unmarried under-21 children of permanent residents are in the F2A category, with about a 2-year wait for visa numbers.If your sister is aged 21 or over, she can also, separately, petition her siblings, who will be in the F4 category, which currently has a 13.5-year wait for visa numbers (longer for people born in India, Mexico, or the Philippines).