What kinds of dimmers do I need?
You could get pretty close to this with three Insteon switches set up:


Switch "A" (the master) connected to line and neutral, load lead capped.
Switches "B" and "C" connected to line and neutral, with the load (light bulbs) connected to the load lead and neutral.
Create a scene where switch "A" acts as the controller, and "B" and "C" are responders.


Switches B and C will operate independently, but any action at A (on, off, bright, dim) will affect both of them.

Edit: @Matthew PK reminds me to point out that this could be any scene-capable smart switch.