Well not an expressionengine member group, but something like this.
CEO registers with custom field (name of their company)
CEO invites employees via email address
Employees are invited and are joined to the company (can only be part of one company)
With an end result on the company having their own page and being able to show the various employees.
I haven’t used the member module at all really so I’m not sure what the best way of doing this is.