As above, the DVC owner needs to make that request. If you rented from two different owners, you’ll need to contact each one, give them the other confirmation number, and ask them to chat/email/call MS to request a “continuing stay” notice be placed on each reservation. Then when you arrive for the first one, go to the front desk and ask whether you’re booked for the same room. If not, that’s the best time to fix it! The resort will want to keep you in the same room just as much as you want to stay there - it saves on housekeeping costs. Have a good trip!