I assume you are asking if family member of yours are allowed to upload images to Shutterstock using new accounts, is that correct?
AFAIK, yes you can do that but you need to contact Shutterstock first. I'm not sure if they will honor the referral commission. But if another person of the fmaily wants to create a new account, that shouldn't be a problem.
Contact SS first, to prevent your account being blocked once they get suspicious about fraud etc.