7. Every American Express card has its own number. Additional cardholder can create separate online accounts, but this is not required. The Basic cardmember can see all activity on all cards. Membership Rewards points from all cards are credited to the Basic cardmember. Initially, transfers can only be made to airline or hotel accounts in the Basic member's name. After the Additional cards have been open for awhile (90 days?) transfers can also be made to their airline and hotel accounts. Membership Rewards points cannot be transferred to any other Membership Rewards account, nor to anyone else's airline or hotel accounts.
I did not know this. Thanks.