You are banned would not be because your family member was banned from using the site. You are banned would most likely be because you also disobeyed one if the rules of Rollbit.

Use the forma above that Ever-young posted for the report.

This is Rollbit official thread which you can also post about it: https://bitcointalk.org/index.php?topic=5326640.0

Let me mention there official account if they will have anything to post regarding this Rollbitcom