Immediate relatives include spouse of US Citizen (USC), minor children (under 21) of USC and parents of USC, provided that the citizen petitioner is at least 21 years of age.
The term “child” includes a legitimate child, a stepchild, legitimated child, illegitimate child, adopted child, and orphan child. Also, the spouse of a deceased US citizen may be considered an Immediate Relative even after the death of the US citizen petitioner.
There is no limit to the number of immediate relative immigrant visas allocated in any fiscal year.