An unmarried child under twenty-one may accompany the investor as a dependant and may study, but not work, and eligibility ends on the twenty-first birthday. Where that birthday falls during the first period of stay, the young person needs an independent status arranged well before it arrives.
Count the children's ages against the period requested
The household's dates and the children's dates rarely line up, and the mismatch is easiest to fix at the planning stage. A child qualifies as a dependant while unmarried and under twenty-one; there is no discretion in the age and no extension of it for a child still in education. A spouse, by contrast, is employment-authorized incident to status, so the second adult in the household usually has options the eldest child does not.
Where a young person intends to continue studying, the alternative is generally an independent student status obtained through an admitting institution, and that takes months. Hypothetical example: a couple buying a garden centre plan a five-year horizon for the business, and their eldest turns twenty-one fourteen months after arrival; his status question needs answering in the first year, not the fourth. Where a young person sits close to that line, the decision about the family's move and the decision about his own status should be taken together rather than one after the other.