Database separation of backend users and member users

I'm creating a website that has 2 kind of users. Backend users and member/frontend users. There are some same functionality on both users.

I'm thinking if it is ok to separate them, instead of putting the two users on 1 table, I will create two separate tables named system_user and member_user. The problem is that do I also need to separate tables that relates to them?

old

new version 1

new version 2

What would be the best way to do this?