I had the same issue - my first two are 15 months apart. I ended up buying a separate monitor so that each has it's own transmitter and receiver. It works perfectly. Both still have monitors in their rooms at 2 and 3 years old. I have my third on the way, so I've been looking into additional options, and I discovered one that has multiple (three I think!) transmitters. I cannot remember the name but will try to sift through my papers and see if I can get that information to you. But if you don't hear back from me, at least know that it's out there. It was a common brand, too, First Years or something l like that. Good luck with your shopping!