Each family member (18 and over) will have their own account, so we recommend each family member having their own device as well. It makes it easier when you don't have to logout/login to access each account. There will also be a family (group) view so you can see how everyone is doing from your account at a high level. You cannot have other people test from within your account; they need their own account. Accounts are free to set up, and so is the app.