Yes, you can. You just need to upgrade to DriveHQ group account service, which is free and comes with 1 free sub-user license.
To become a group account, please logon www.drivehq.com, go to My Account, then click on Group Account. After you have upgraded to a group account, you can click on the Group Admin link to create/add/edit/delete/disable sub-users. You can create different types of sub-users and sub-groups.