US citizens are permitted to obtain legal permanent residency for immediate relatives including spouses, parents and children.
If the marriage on which the immediate relative relationship is based is less than 2 years old, the spouse and any children will receive conditional permanent residency.
An immediate relative child has to be under the age of 21 and unmarried. If the citizen parent files the I-130 visa petition before the child’s 21st birthday, the child’s age is frozen at 20 years even though the child will be 21 years of age or older when he actually receives his green card. There are special rules for step-children and adopted children.
In order to sponsor an immediate relative parent, the sponsoring son or daughter must be at least 21 years of age.