They are from the same family as the western Browns, both Dugites and Gwardars hatchlings do look alike in some areas.
There are places where dugites and gwarders can be found in the same habitat, for example the Swan Valley. I have not heard of any interbreeding of the 2 species, but not saying it hasn't or can't happen.
If it did happen, I don't think we would much to any differents in distribution between the two species as you can sometimes find Dugites having 2 or 3 postocular scales... thats my thoughts anyway.