1) If you’re applying as a family unit, you must apply together. The main applicant who is a BN(O) should apply first and get their unique reference number. Any family members applying will need to quote this unique reference number in their applications.
2) If your family members do not apply with you, they will not be able to apply for the Hong Kong BN(O) visa to join you later.
3) Children under 18 should apply with both of their parents, although there are some exceptions.
4) If you or your family members travel at different times to the UK, you may not all qualify to settle in the UK at the same time and may have to make further applications for permission to stay in the UK to meet the 5 years required.