Can I pair a new baby unit to an existing parent unit?

Hi

You could try but I doubt that it will work.

I think that these units are somewhat like wireless keyboards connected to a PC. The receiver plugged into the PC and the keyboard are already paired by the manufacturer. I think it is the same with the baby monitor as there is nothing required to "set up" the connection between the two units. Simply plug both units in and they should connect.

This is to prevent interference from other identical devices or to prevent access from other identical devices using the same system. In your case you wouldn't want someone else having the same unit having access to your system.