https://www.gov.uk/british-national-overseas-bno-visa/apply-from-outside-the-uk
If your application is unsuccessful
If you’re a British national (overseas) and your application is unsuccessful, your family members’ applications will also be refused. If your application is successful but your family member’s is not, you can still come to the UK.
You’ll get a refund for the healthcare surcharge you paid for each unsuccessful application.