That is unless you live in self-contained accommodation, separate from your parents. This is what the tv licensing people sayabout lodgers:
If you watch TV in your room, you need a separate TV Licence.
This is the case unless you have a relationship with the licence holder, for example if you are:
A member of the family
A common law partner
A live-in employee such as a nanny, au pair or housekeeper.
Please note: if you live in self-contained accommodation such as a separate flat or annexe, you will need your own separate TV Licence regardless of your relationship with the home owner.