Family Sharing Fraud?

My parents have newish I phones. I was reviewing their family sharing status. There is a "family member" by the same name as their grandson, but that person has an e-mail address that none of us are familiar with. I am VERY concerned that this is fraudulent. How do we go about removing a "family member" that is supposedly THREE, has an e-mail that we are not familiar with, and get their status sharing in our family removed?