Names, including what people call each other, are an interesting element in Franz Kafka's The Metamorphosis. In fact, we only know the first names of two characters: Gregor Samsa and his sister, Grete. All of the other characters are referred to either by their relationship to Gregor (as in "Gregor's father") or by a description (as in "the cleaning woman"). This is obviously a deliberate choice by Kafka to enhance the theme of Gregor's alienation and isolation in this story.
Every character in the story knows Gregor, even the three boarders who eventually come to live in the Samsa house; yet only two people ever use his name in direct address: Gregor's supervisor from work and Grete. His supervisor calls him "Mr. Samsa," and Grete only directly utters his name once, in anger.
"Gregor!" shouted his sister, glowering at him and shaking her fist.
By the end of the story, even Grete, the one who seems to care the most for Gregor, refers to him by his title (brother) or, even worse, by the pronoun "it."
"Father, Mother", said his sister, hitting the table with her hand as introduction, "we can't carry on like this. Maybe you can't see it, but I can. I don't want to call this monster my brother, all I can say is: we have to try and get rid of it. We've done all that's humanly possible to look after it and be patient, I don't think anyone could accuse us of doing anything wrong."
Throughout the story, people talk about Gregor but not to him; people who actually communicate with one another generally use people's names when they talk, but this family does not. The narrator talks about the Samsas only by their relationship titles (mother, father, sister), suggesting that they are not important except in their connection to Gregor. The boarders have no names because they have no connection to Gregor except as usurpers in his home.
By rarely using proper names in this story, Kafka highlights the lack of personal relationships despite the presence of familial connection. This social and relationship isolation Gregor experiences mirrors the the physical isolation he experiences after his metamorphosis. Though Gregor's body changed, tragically, his relationships with his family remained the same.