Robert is most similar to Victor in his drive to explore the world. He is also similar to the monster in his feelings of utter aloneness and his desire to have some kind of friend. It’s almost as if he’s the common link between them metaphorically. How appropriate, as he is literally the common link between them at the end of the text.
But Robert isn’t exactly like Victor, either. (He’s a foil, not just a reflection.) While Victor’s explorative tendency leads him to self-destruction and death, Walton chooses to cut short his search for knowledge in favor of life – both his and his crew’s. This stands in direct contrast to Victor’s ultimate sacrifice of his whole circle of loved ones for the greater good, first of science, and later of humanity. Heavy stuff.