That doesn't make a "Family Account" though. Many FFPs have a programme whereby members sharing an address or a family relationship can pool their miles at no charge. FB (like the vast majority of FFPs) does not have this.

You can transfer miles, as I said above, without having to pay for two(or more) American Express cards. There is a fee, but unless you are transferring millions of miles, it will still be cheaper than ordering and paying for credit cards, which are only available in a limited number of markets anyway.