I am not trying to be pendatic here, but to make a distinction the "Dog Brothers" usually refers to the group of people who show up at Gatherings and fight, those of us who do so who then get invited into the "Tribe." There is no fixed standard or curriculum for this group, aside from having a certain amount of experience you get people from a wide variety of backgrounds, so you can't really say that a "Dog Brother" has any sort of counter knife experience.
Now Dog Brothers Martial Arts is a curriculum put together by Marc "Crafty Dog" Denny to produce a well rounded fighter. That curriculum while heavily based in FMA has lots of other influences, Krabi Krabong, BJJ, etc etc. It has elements of the dueling that DB got its rep from but also more real world type stuff like unarmed vs knife. He absolutely has a curriculum of knife defense, his knife offense isn't public and he really hasn't publicly shown too much that I have seen about dealing with the knife in a ground grapple. I have no doubt he has an approach, but he is leery about putting his knife material out for public consumption.