Sure, it's fine and permitted by the program rules. I have done this many times for extended family when we have done group vacations together. If you're not planning on paying for all of the incidentals on both rooms, you should have your family staying in the second room switch it over to their credit card. Side note, you're only entitled to titanium elite benefits for the room your occupying. If you ask nicely, the hotel may also grant elite benefits to your second room with your family as a courtesy. If they do, they are going above and beyond the program requirements. Enjoy your trip!

--Jon