Zerodha does not allow existing account holders to open an account for a family member or friend using their registered mobile number and email ID. It would be easier for clients to track communications and reports that are shared from the exchanges, depositories and Zerodha when unique contact details are provided.
However, clients can use the existing contact details to open a non-individual account, i.e. HUF, partnership, corporate account etc. To learn how to open a non-individual account, see How to open a non-Individual account with Zerodha?