A spouse and unmarried children who are under twenty-one may be included as derivatives. An adult child or a married child cannot be, and each derivative is assessed on their own admissibility. Where a child is close to twenty-one, the age calculation is technical and should be assessed rather than assumed.
Age and marital status divide the household, and timing can move the line
Derivative eligibility reaches a spouse and unmarried children under twenty-one at the relevant time. That produces uncomfortable outcomes in families where the children are only a few years apart: one may be carried on the petition while an older sibling has to find an independent route entirely. Because processing periods vary and statutory age protection can affect the calculation, a child in their late teens should be assessed by counsel rather than by counting birthdays, and the family's own timetable should drive when the petition is filed even where the commercial timetable would prefer to wait.
Two further points follow for planning. Derivatives receive the same conditional permanent residence for two years, and their conditions are removed alongside the investor's on Form I-829. And permanent residence is not citizenship: naturalisation is a separate process with its own residence and eligibility requirements, and nothing in the investment shortens it.