If I understand correctly, you’ve already set the collision response settings of the trigger boxes (the ones attached to your characters) to ignore each other but overlap the characters collision, and the problem is that the trigger boxes still collide with one another?
If that is the case, you should search for the ‘Auto Weld’ setting under the physics category in the details panel with your trigger box component selected, and disable that, so that your component does not inherit collision profile from the root component.