Yes, it is possible.
To do so:
- Log in to the registration site here.
- Click on the "My Account" button at the top of the page.
- Go to the "Hotel" section.
- Enter the first and last names of the people you wish to share your accommodation with, in the boxes provided. In order for this wish, to be taken into it is imperative that these people are on the same offer as you and mention the same names as you.
If you do not enter this information, you will be randomly allocated to a hotel room according to your gender/nationality/language.