Aunt
The opposite relationship of uncle would be Niece or Nephew.(The opposite gender is aunt.)
Sister-in-law describes a female. Brother-in-law describes a male.
The opposite gender of uncle is aunt.
uncle
There is no such thing as an "opposite" of a great uncle. The female form of great uncle is great aunt. The person to whom you are a great uncle is your great niece or great nephew, depending on their sex. None of these are opposites.
possibly, aunt
Niece would be an opposite as a niece is female and a nephew is male.
The opposite gender of a great uncle is a great aunt. A great uncle is the brother of one of your grandparents, while a great aunt is the sister of one of your grandparents. Both terms refer to relatives in the same generational level within a family tree.
Just the opposite, the novel inspired people to oppose slavery.
The opposite of "Avuncular" is "Materteral". This means "suggestive or characteristic of an aunt", just as "avuncular" means "suggestive or characteristic of an Uncle". The stem of the word, "materteral" is "matertera", L. for "mother's sister". Ref: Yahoo answers Malcolm R. Printer
The word "aunt" stays the same in Australia. "Aunty" is also used in Australia. The word for the opposite gender of Aunt is Uncle.
The brother of your aunt's husband is not your uncle. Also the brother of your uncle who is not your uncle is your father.