The easiest way is to connect the pair of LEDs with their 50% resistors (14-10) = 4/.5 = 8 ohms straight of the ignition wiring, so the LEDs are on 50% when the engine is running. Now wire a diode to the brake lights (anode to lights) to its cathode connect two four ohm resistors, one to each LED.
Theory :- without the diode, the voltage on the LEDs in normal running would backfeed and make the brake light bulb glow, the diode stops this. the diode must be rated at 2 A and 12V - cheap device.
Frank