What is your nan's sister's son to you?

Answer 1

Probably your niece-in-law.

Answer 2

If by "your nan's sister's son" you mean "your mother's sister's son", he is your 1st cousin.

However, "Nan" is often short for Nanna, meaning grandmother. Your grandmother's sister's son is your parent's first cousin and your first cousin, once removed.

Answer 3

AnswerGreat Aunt...unless she only put 5$ in a card, then she is a not-so-great-aunt AnswerYour grandmother's sister is your great aunt and your daughter's great great aunt.

Answer 4

Well if she is your father's sister then that makes her your Aunt. Then if your Aunt has kids that makes her kids your cousins.