Mahoney brought immense poignancy to the role. In one episode, Frasier and Niles turn against Marty, believing that he once had an affair. It transpires that it was their mother who had been unfaithful, but out of respect for her, Marty had not wanted to taint the boys’ memory of her. Protecting his sons from harsh realities that might hurt them – the role of a fine father – is another aspect of this rich character.