Sister's son is referred to as "ભત્રીજો" (Bhatrijo) in Gujarati. This term specifically denotes the son of one's sister. In Gujarati culture, family relationships are significant, and such terms help in clearly identifying one's relatives.
cousin
Your father's sister is your aunt and her son is your first cousin.
Your sister's son is your nephew His sons are your grandnephews, and his daughters are your grandnieces.
Well, it depends how close you are to your husbands family. If you really want to know they are cousins-in-law.
your second nephew
Your sister's son is her grandson and your great nephew. Some use the term "grand nephew."
Your sister's son is your nephew His sons are your grandnephews, and his daughters are your grandnieces.
Jijaji- brother in law
If your niece's is by your sister but the brother is by your sisters new husband & another woman there would be no blood relation. If not then he's the nephew
There are different words depending on whether it is your brother's son or sister's son. Bhanej and bhatrijo.
If two people are brother and sister and the sister has a son, then: her brother is her son's uncle, and her son is her brother's nephew.
Your son would be the uncle of his brother's son.