Family terms are set by the official framework itself and must be read from the current official source rather than assumed by analogy to other categories.
Do not import rules from another route
Hypothetical example: It is tempting to assume that a spouse and unmarried children under twenty-one are included, because that is the pattern in the employment-based immigrant categories, and that a spouse would be able to work, because that is true in some nonimmigrant categories. Neither assumption should be carried across. The official material governs who may be included, on what terms and at what cost, and those provisions have their own logic. Where a family's plan depends on a spouse working or a child studying, the safest approach is to confirm each of those points explicitly against the official source, in writing, and to have a fallback in mind if the terms turn out to be narrower than expected.
Treat family eligibility as a current, person-by-person question rather than assuming it follows automatically from an applicant's payment. Hypothetical example: A tool-and-die shop owner has an adult child who is financially dependent but married. The household must read the official terms for the exact family category, then decide whether the child has an independent route. An applicant-paid transfer into the U.S. government does not itself settle another adult's immigration status.
Avoid accepting a household description from an intermediary. Confirm each relationship and eligibility issue under the official terms in force at the relevant time.