After some controversy, it has been shown that subharmonic voltage (phase) locking does not exist in the ac-driven overdamped resistively shunted junction model of a Josephson weak link. We predict that for a very similar system of a pair of coupled links without ac drive, mutual subharmonic locking can take place. We demonstrate our thesis both by a careful numerical simulation of the exact equations of the model and by a second-order analytical perturbation calculation based on the coupling parameter
