Only admin of family tree needs register. Members of family tree do not need register because they are created by admin.
You have to use your email to register. If you do not have email, register free email of any email provider such as
Gmail You should use your real email to register because if you forget your password you can request the system to send your password to your registered email.
You have to define 2 passwords The first password is a password of family tree admin. It is used to login BigFamilies as an admin of family tree. The second password is a password of members. It is used to login BigFamilies as a member of family tree.