Are "fetter" and "kusine" used interchangeably, or does fetter only ever refer to male cousins?

Seeing as "fetter" only refers to a male cousin, I assumed "nephew" would also be an acceptable translation. It was not accepted, though. Is this due to a misunderstanding on my part or an oversight on yours? And in case of the former, what would be the correct translation of "nephew" in Norwegian?

Was marked incorrectly for writing an aunt, yet that appears as the correction in the translation