Published family rules cover a spouse and unmarried children under 21. For a first application contemplated at 22, do not assume derivative eligibility. Have the legally relevant age and any applicable CSPA protection assessed on the case facts; if derivative eligibility is unavailable, examine an independent route without assuming its outcome.
Test the relationship as it is, not as you hope
Take a household where the parents intend to fund a hypothetical manufacturing project in Michigan and want all three children included. Two children are 15 and 19 and unmarried; the eldest is 22. The first two are examined as derivatives; the eldest is a separate question with a separate answer. Ask the official instructions how each person is to be included before you commit any figure to a spreadsheet.
The published result still depends on the appropriate EB-1 or EB-2 eligibility, admissibility and visa availability. TN eligibility turns on Canadian or Mexican citizenship, a listed profession and a prearranged professional job; it has no bearing on whether the other spouse can apply under the Gold Card framework. Payment evidence establishes a financial event, not the complete EB-1 or EB-2 eligibility, admissibility or visa-availability decision.