I found this on the net.
I would say that the part I have highlighted in red, can be understood as an address where you can be contacted, so a parents address, brother etc should be OK, as long as you can be contacted through the address.
The letter I found :--
Driver and Vehicle Licensing Agency
Drivers Customer Support
D12
DVLA
Longview Road
Swansea
SA6 7JL
Dear Mr Jackson
Thank you for the e-mail of 11 July requesting information under the Freedom of Information Act 2000.
You asked
What information DVLA holds in relation to dealing with drivers of no fixed abode and vehicles registered to same.
DVLA holds no information and provides no advice to drivers of no fixed abode. The same applies to vehicles. It is not possible to issue a driving licence or a vehicle registration document unless we are provided with a residential address at which the driver and/or vehicle keeper can be contacted. This is required for law enforcement purposes by the Police and by DVLA.
Note: Post Office boxes are not considered viable address details as in the event of an emergency the authorities i.e. police would not have an address to contact the driver. Secondly it also increases the risk of fraud. Post Office boxes can be rented for a short time and the person then become untraceable.
