Yes, but with conditions. You do not need to be 18 to initiate the promotion, but you must be the adult organizer of the Microsoft Family Group that owns the child account.
Even if technically possible at 13+ (varies by region), wait until actual adulthood (18). The transition brings real-world responsibilities (purchases, contracts, data privacy, online conduct) that minors aren’t equipped for. Use Family Settings to gradually grant autonomy instead.