The Dark Mirror (1946)
Same characters: The hero is a psychiatrist in love with one of the two twin sisters (one is good, the other is evil).
It is referenced
When the 1000 identical robots are asked which robot in the formation does not belong, they all answer "One of us", the same answer Terry and Ruth Collins replied when asked who went to an outing and who rested home. Both are a kind of "concealing situation" between twins.