Use the AUX from both motors in your logic as the "latching" bit. When the starters drop out, your logic will update and turn off the output.
For drbitboy's question:
Use the AUX from the starter of the 1st motor as the enable for the 2nd and add a maintenance bypass switch in case the 1st motor is out of service and you want to run the 2nd one.
Makes me wonder how big these motors are.....