Answer: Yes, Nick Carraway is an unreliable narrator in the Great Gatsby.
Step-by-step explanation:
The reason why Nick is an unreliable character is not simply the fact that he is Daisy's cousin. Even though he is observing and narrating someone else's story, Nick is a first-person narrator. He is one of the characters in the story and the plot is told from his point of view.
A first-person narrator has limited knowledge of what is happening and tells the story according to his own view and opinions. Thus, what the reader gets to know is what the narrator also knows. In this case, Nick despises his own cousin Daisy, her husband, and her friends for being shallow people with no values. Despite Gatsby's being a criminal, Nick admires his pureness of heart and childish ambition. Therefore, that is what readers are told about the characters.