When you perform a group registration, if User Registration Integration is enabled on your Events Booking installation, Events Booking will only allow creating user account for the billing person, not for group members. If you want to create separate user account for each group member, you can enable and use Events Booking - Group Member Account plugin.
This plugin only work for Group Registration. So if you collect members information in shopping cart or ticket types, there will be no user account created.
In Joomla, to create user account, we need to have following information :
You should have at least first_name field (or both first_name and last_name fields) collected for each group members. That data will be used to populate name of the user account.
Make sure email field is collected for each group member. Without email, there will be no user account created
4. Password
This is controlled by Password Data parameter in the plugin.
If there is an existing user account with the username or email, the system won't create a new user account. It will assign the group member record to that existing account instead