A spouse and unmarried children under twenty-one may be included as derivatives, but derivative status is permanent residence too, with the same expectation of living in the United States. A family that remains in Canada while one member holds the status faces the same abandonment questions, multiplied across each person included.
Decide together, because the status is the same for everyone
Households sometimes imagine that one member can hold the status for the family's future benefit while everyone continues life in Ontario. That is not how the status works, and every person included faces the same obligations. Have the conversation explicitly: who intends to live in the United States, when, and what happens to schooling, work and the Ontario business in the meantime. If the honest answer is that nobody is moving for several years, the sensible course is usually to wait until the plan is real rather than to obtain a status that will be difficult to keep. Where children are approaching twenty-one, that timing pressure is real, and it should be weighed openly against the readiness of the rest of the plan.
Hypothetical example: a Tyendinaga textile-recycling entrepreneur intends to invest with a spouse and an unmarried twenty-year-old child who is considering marriage. Identify the family members who can be included before the investment timetable is fixed. Marriage or aging out changes derivative eligibility and may require an independent path. Keep civil records current and make the family decision alongside the commercial decision, not only when an interview is scheduled. The file should not assume that financial support or close family relationships overcome a category's express derivative limits.