Only unmarried children under 21 qualify as derivatives, with age protection under the Child Status Protection Act in some circumstances. A married or older child cannot be included and would need a separate basis.
Derivative status stops at 21 or marriage
Hypothetical example: Nora and Tom's son already lives in the United States on his own status and is over 21, so he cannot be a derivative on their petition. If they had a younger child, that child could be included provided the child is unmarried and under 21 when it counts. The Child Status Protection Act can freeze a child's age using the time the petition was pending, which matters when adjudication takes years, but it does not help a child who was already 21 at filing. Derivatives receive the same conditional residence and must join the I-829 filing or file separately. Because the parents will be permanent residents, they may later sponsor a married or adult son or daughter in a family-preference category, but those categories carry long waits shown in the Visa Bulletin. Their own Canadian citizenship is not affected by becoming U.S. permanent residents, though residence obligations and tax filing in both countries need planning.
Hypothetical example: A cheese-export business owner plans an EB-5 filing with a spouse and an unmarried child who will turn twenty-one during processing. They should document the child’s birth date, expected filing date, and each stage that affects the age calculation. Civil records settle the relationship and age; informal plans to join later do not. Because the principal’s investment does not preserve derivative eligibility indefinitely, the family must decide early whether another independent route may be needed.