So I have 1 circuit with 6 branches in it
They get turned on by another source at variable times. I'd like something that will open one branch when another closes but I cannot think of it.like a relay but smaller since I'm not sure voltage but could be very low and amps are very low.
Three options come to mind:
Relays. Use a small signal relay with its NO and NC contacts to build relay-logic.
Analog Mux. If the current is very low, then there are "analog switches" ICs that can be controlled with a microcontroller (Arduino) or even digital logic.
Transistors. Similar to #2, but with discrete transistors setup as high-side switches.