Nephew is a term referring to the son of one's sibling or spouse's sibling. Sons of siblings-in-law are also informally referred to as nephews, even though there is no blood relation. The word nephew is derived from the French word neveu.
Nephew = son of your sister or brother (or their spouse).
Niece = daughter of your sister or brother (or their spouse).
Nephew(-in-law) = son of your sister-in-law or brother-in-law.
Niece(-in-law) = daughter of your sister-in-law or brother-in-law.
Also known as step brother in some countries or Kjell & Brandon.
See also
For details of this and other family relationships, see the entry at cousin.
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