The official FAQ describes a spouse and unmarried children under 21 as eligible to accompany the principal, each with their own gift and processing fee. A 23-year-old son is outside the described family group and would need a route of his own.
Price the family by the person and check the ages against the calendar
Hypothetical example: the contractor's wife and their daughter of seventeen intend to move; their son of 23 does not and could not be included in any case. The official FAQ, as read on the review date, states an additional gift and processing fee for each accompanying spouse and eligible unmarried child under 21, so the household figure is three gifts and three fees, not one. The daughter's age also creates a deadline: she is eligible as a child now, but the immigrant classifications the program uses are subject to visa availability and processing time, and whether protection under the Child Status Protection Act would apply to her should be asked of counsel rather than assumed.
The son can visit as a Canadian citizen, study on a student status, or later be sponsored, but the family's plan should not be built on an assumption that he follows automatically. Each included person must separately be admissible and pass vetting, and each needs the same identity, background and prior-history documents as the principal.