This was a while ago.
My wife has her own Centurion card (titanium) with its own number. I seem to recall that we were initially offered only the 2 centurion cards but when I explained to our RM that we need more ( each wanted a personal and a business), they gave us extra cards. That was not enough as the titanium card would not "tap" so when I complained about this they sent me a 5th centurion card which was not tinanium and does work with tapping.
This is all one account with separate sub-accounts. We have since loaded the cards onto our phones so the cards rarely come out.
My RM was extremely helpful and flexible, so perhaps I was lucky.
Since I started with Centurion, I have only ever dealt with one RM who knows me and my preferences very well - I think this continuity is one of the most beneficial aspects of Centurion.