My brother and I have pretty solid evidence that my paternal uncle is my real father, not my “dad”. However our mother (who divorced “dad” long ago) denies it, and there isn’t really a way of getting DNA from “dad” or my uncle to do a paternity test.

We have been wondering how related to each other a DNA test (such as from 23andme) would show we are. I know it’s straightforward to detect if people are half-siblings or full siblings with these tests, but is it possible to distinguish half-brother+cousin from full brother? Or would there simply be too much overlap in the potential range of shared DNA between these two levels of relatedness to get a conclusive result?