The initial review should identify relationships, ages, marital status and who intends to join the principal applicant.
Do not use a household shorthand
The official FAQ describes spouses and unmarried children under 21. Ask immigration counsel to assess your actual family circumstances and identify anyone needing a separate strategy. Do not infer that financial dependency alone establishes inclusion, or that paying for a relative resolves an eligibility issue.
Resist household shorthand at every stage, because terms like the family, the kids and my wife's mother conceal exactly the facts that determine the answer. Convert each into a named individual with a date of birth, a nationality and a documented relationship. Then establish, against current official materials, which relationships the programme's terms actually recognize at the initial stage and which it does not.
Ask specifically about relationships that are common in practice and frequently unaddressed in summaries: stepchildren, adopted children, children in the care of one parent following a separation, and partners whose relationship is not registered. Where a relationship is recognized but the documentation is thin or held in another country, that is a task to start now. And remember that admissibility is assessed individually, so each person's own history matters regardless of the household's arrangements.